Pre AEW, Jericho was only ever considered an all-time-great by contrarians who wanted to prove how smart they were by saying someone who was never the guy was actually one of the best to ever do it.
When he first showed up at AEW, suddenly he went from an underrated but good guy to a lot of fans to "THE UNDISPUTED GOAT", as a way to boost the legitimacy of AEW.
The truth is that Jericho never was, and never will be the GOAT. He's undoubtedly a hall of famer, but he's never had 'it'.