I have quoted 3 sources below on this topic.
Basically, it says that in Sri Lanka and other Theravada countries, people who lived over 150 years ago, thought that even stream entry was no longer possible because in-depth understanding of meditation had been forgotten. They felt that it's better to practise virtues and make merit, while waiting for the next Buddha, Meteyya or Maitreya to come and show them the path to Nibbana. Supposedly, even Buddhaghosa, who authored the Visuddhimagga around the 5th century CE in Sri Lanka, held this view.
However, Buddhist meditation practices (based on the Satipatthana Sutta and Visuddhimagga, as well as other suttas) started to be revived in Burma as a popular movement, over a hundred years ago, and then spread to other countries including Sri Lanka. This seemed to have reinvigorated the faith of Theravadins (both monks and lay people) in the possibility of stream entry and enlightenment.
Here, Buddhism did not become extinct in Sri Lanka, but people simply lost faith in the possibility of attaining even stream entry, until Buddhist meditation was reintroduced to them from Burma.
In the Broken Buddha book, S. Dhammika wrote:
In Sri Lanka it is widely believed that it is not possible to become
enlightened anymore and it’s not just simple folk who believe this
either. I once attended a talk by the famous Narada Thera of
Vajirarama in Colombo during which he said that it is even
impossible to become a sotapanna today. Richard Gombrich found
this same idea to be widely held in Sri Lanka. ‘The
comparative rarity of meditation is closely connected with the
widespread belief in the decline of Buddhism. A village girl said
that in a Buddha-less period one must keep trying, but only
limited progress is possible. It is further believed by the
majority of monks, at least those whose general attitudes can
be described as traditional, that the sasana has already
declined so far that it is no longer possible for men to
attain nirvana. This opinion is very prevalent among the
laity...One monk even specified that till (Metteyya) comes it
is not even possible to become a sotapanna. The last arahat is
commonly said to have been Maliyadeva (1st cent B.C.E). Others say
that there may still be human arahats, but it is unlikely
and/or undiscoverable ....
I have heard these same views expressed a thousand times in Sri Lanka.
Even Buddhaghosa did not really believe that Theravada practice could
lead to Nirvana. His Visuddhimagga is supposed to be a detailed, step
by step guide to enlightenment. And yet in the postscript he
says he hopes that the merit he has earned by writing the
Visuddhimagga will allow him to be reborn in heaven, abide
there until Metteyya appears, hear his teaching and then
attain enlightenment.
In Encyclopedia of Buddhism (editor: Robert E. Buswell, Jr.), it is written:
By the tenth century C.E., vipassana meditation appears to have fallen
out of practice in the Therevada school. By that time it was commonly
believed that the religion of Gautama Buddha had so declined that
liberation through insight could no longer be attained until the
advent of the future Buddha Metteyya (Sanskrit, Maitreya) many eons
from now. In the early eighteenth century, however, renewed
interest in the Satipatthana Sutta (Discourse on the Foundations of
Mindfulness) led to a revival of vipassana meditation in Burma
(Myanmar). After encountering initial resistance, the practice of
vipassana was endorsed by the Burmese sangha and embraced by the
royal court.
By the late nineteenth century, a distinct praxis and organizational
pattern had emerged that set the stage for the modern vipassana
movement of the twentieth century. Led chiefly by reform minded
scholar-monks, a variety of simplified meditation techniques
were devised based on readings of the Satipatthana Sutta, the
Visuddhimagga (Path to Purification), and related texts. These
techniques typically follow the method of bare insight.
The
teaching of vipassana also prompted the development of new
Buddhist institutions called wipathana yeikthaor insight
hermitages. Initially attached to monasteries, these evolved into
independent lay oriented meditation centers. A related development was
the rise of personality cults devoted to the veneration of
prominent meditation teachers as living arhats. In terms of
impact, the popularization of vipassana represents the most
significant development in Burmese Buddhism in the twentieth
century.
Thailand has also witnessed a revival of vipassana practice in the
modern period, and both Burmese and Thai meditation teachers
have been instrumental in propagating vipassana in Sri Lanka,
India, and the West.
In Meditation en Masse, Erik Braun wrote:
These days many assume that Buddhism and meditation go hand in hand -
sometimes they are even considered to be one and the same. But even
counting Theravadins, progenitors of the massively popular insight
meditation (Vipassana) movement, relatively few Buddhists historically
have ever understood meditation to be essential. On the contrary,
instead of meditating, the majority of Theravadins and dedicated
Buddhists of other traditions, including monks and nuns, have focused
on cultivating moral behavior, preserving the Buddha’s teachings
(dharma), and acquiring the good karma that comes from generous
giving. To be sure, such folks have recognized the critical role
meditation plays in awakening—in the Theravada view, you cannot become
enlightened without such practice—but they have not doubted that one
can live a worthwhile and authentic Buddhist life without meditating.
Aiming not toward awakening but toward a good rebirth, many
Theravadins have even argued that meditation is inappropriate in our
degenerate age, except perhaps for a rare few living in the isolation
of jungles or mountain caves. Where, then, did this now pervasive idea
come from that meditation lies at the heart of Buddhist life?
This question brings us to Burma just over a century ago. Prior to
this time, no trend toward widespread meditation had developed
anywhere. It is true that Thai forest masters, above all Ajaan Mun
(1870–1949) and revivalist figures in Sri Lanka such as Dharmapala
(1864–1933), played an important part in the establishment of insight
practice and sounded the call for lay meditation. But they did not
spark any broad-based movements. One must look instead to Burma to
account for the ascendance of meditation to a popular
practice—specifically, that of insight meditation. The Vipassana view
understood meditation as the logical and even necessary application of
a Buddhist perspective to one’s life, whether lay or monastic. The
rise of this practice, however, was not strictly an indigenous
development. It came into being specifically through colonial
influence. (In fact, no current tradition of insight practice can
reliably trace its history back further than the late 19th or early
20th century.) Though now a global movement, insight practice had its
start in a moment of interaction between a Western empire and an
Eastern dynasty. Indeed, one could go so far as to pinpoint its
origins to a particular day: November 28, 1885, when the British
Imperial Army conquered the Buddhist kingdom of Burma.
