#4. He's a proven top star
When AJ Styles arrived in WWE, he himself admitted that he expected to be in the midcard. However, the cream always rises to the top and by a combination of hard work, incredible skills, listening to the advice given to him and using it along with being one of the best in the world, it didn't take too long for Styles to prove that he belonged to the top.
As a result, he received a push sooner than later. A few months in, he was main eventing consecutive PPVs, competing for the WWE title. After that, he feuded against (and defeated) the former face of the franchise in John Cena. He would become WWE Champion less than 9 months within his debut, and despite his United States title runs in 2017, he has always consistently been a main event player.
The fact that he has been featured so heavily shows it.