I just listened to The Beast of Langeais episode, quite chilling for an episode dedicated to, possibly, a wandering goat!
A few thoughts, there is mention of a moat, but I dropped into Google streetview, and there is no moat - this is a raised drawbridge in the sense that to enter the castle, you have to climb steps to reach the drawbridge, so the idea of the lads sleeping in the moat, and (as suggested by the sceptic) being essentially sleeping in a drain below the water table, while logical when imagining the account, actually makes no sense. It is not the case that the moat is recently filled in either, since looking at the links posted by
@AmStramGram shows that the approach is essentially unchanged.
Secondly, Danny mentions things like, "Well, would an experienced police officer confuse the smell..." etc. The point here is that the witness is an experienced police officer
now, but wasn't at the time, so had no basis for comparison.
The whole experience sits very much in the 1970s-1980s mindset, with much fear of devil worship etc. reflected in the media (for example in the
Omen films and Satanic cult panics).
I also assume that the portcullis was lowered, or the main gate shut, or the lads would naturally have slept in the castle, so a wandering goat couldn't have just climbed the steps and entered the castle, explaining its disappearance.