#4 A ceiling for his character in WWE
Remember just how popular Tye Dillinger was when he debuted at the number 10 spot in the Royal Rumble? The crowd was behind him and they showered 'ten' chants on him. And then, in a matter of no time at all, he got lost somewhere in the mid-card.
WWE has operated with a certain character for their top guy in mind. There are anomalies like AJ Styles and Daniel Bryan, but both of those individuals are exceptions to the norm and not the norm itself, sadly. The top guy has always looked like John Cena, Batista or Randy Orton.
Had Tye Dillinger stuck around in WWE, he would probably have had a job for a very long time, but wouldn't have been able to establish himself as a top guy. And this reality may have dawned on him before his WWE departure.