I'm not trying to be disrespectful, it's just that it seems like the
act of disrobing is sort of a rejection of Buddhist teachings.
Atma would say it a reaction of a proper observance and even formally one needs to express the renunciation from one of the Juwels.
It's is totally right, to have doubt in such a case and being a teacher after having been monk, sometimes is just a livelihood by teaching the Dhamma, which is actually very against Buddhas economy and the ways he kept it protected from being corrupt.
There is no, no old story of a person who renounced the holy life to start to be holy.
One needs to say, that a Monk or Nun, does not make his training to be a teacher, nor do they have a duty to teach. The only real duty is the practice the path. So teachings are always "just" generosity and without strings (if followed the Vinaya).
There are case, where people argue, that they would violate the Vinaya to much, when actively teaching people in broad. Or some say, its not possible to live a monastic live today...
Arguments are many and of course, the "cheap" course of training to gain a livelihood incl. some reputations for it, is very usual today, especially under Western Teacher.
Its no time wrong and for nobody, to give the gift of Dhamma. It's wrong for everyone, may one be a monastic or a Layperson, to receive anything in return for Dhamma.
There was shortly a famous teaching monk in Thailand, for many many years, who felt in love and spontaneously left the monk hood, leaving 10.000s of devoted people behind and caused surely a lot of faith to decay.
Actually its 90% a matter of not being able to live an abstinent live. Since nothing is for sure, there are some very inspiring stories from Ajahn Chan in regard of such monastic matters. Food for the Heart
On the other hand, for example, two of the leading teachers here in Cambodia are Exmonks, both, one of them with a million following, are said to live actually a very Vinaya-Standard live.
One actually has an easier way to use gain for a certain plan.
In regard of your idea about, that they can not be enlighten, that's right, even if they would live without wife. It's merely in the other direction. Someone who gains the highest fruit would leave house, even if gained as householder and if there is no way to do so or no Sangha available, one would die within some days.
The Buddha gave drunkenness as the only reason to go back to the lower life. Drunken with youth, health, and or life.