They thought enough of him to give him a match against Cena at Mania in 2014, and be the champion at Mania in 2017, and have the Wyatt Family utterly thrash The Shield, perhaps the company’s most popular faction ever.
He lost to Orton as the champ in 2019, even after Cena himself had insisted Wyatt should win the title off of Cena just months before.
The Wyatt Family never really grew to be the dominant faction, even with the massive talent of Wyatt and Lee (then Luke Harper).
While Bray and the Wyatt Family were always lingering around the top of the card, their time in the marquee was only brief.
That ignores what Wyatt might want to do and the myriad reasons he might not want to do that, what Lee’s family might want, and everything else that goes into it, as tidy a story as that might make.
Wyatt certainly would be welcome in AEW though, and he might relish the chance to fully flesh out the characters that were cut off just short of being magical by WWE.