Conner has gotten beaten up every fight since Jose Aldo i think. The hype train comes to an end.
I don't think being unbeatable or untouchable was ever part of Conor's appeal though - quite the opposite, in fact.
The UFC has had a whole heap of "unbeatable" champions over its history - Aldo, Mighty Mouse, Joanna, GSP, Anderson Silva, Jon Jones. They didn't all draw well, and
none of them drew like McGregor.
A big part of that, IMO, was that you didn't really need to watch their fights: you knew who was going to win, and you had a pretty good idea what it would look like. Jones would probably do some violent shit, so that was worth watching. Silva would probably do some comical shit, that was worth watching. GSP was gonna jab - a lot. Aldo would outboxm, pivot and stuff takedowns, it was masterful, but the majority of people obviously thought it wasn't worth watching. Joanna and Mighty Mouse would almost certainly style on their opponents on the way to a decision win - people obviously didn't think that was worth watching either, their loss.
Conor, on the other hand: as soon as he started in title fights and main events, he became interesting specifically
because he could lose. You needed to tune in because anything could happen, and it'd probably be entertaining to boot. You still would, if he "unretires", because whoever he fights next you know he's in with a real chance to win AND a real chance to lose.