Some superstars are shaken mentally after being called to RAW/SmackDown and experiencing adversity regarding the ability to get over
Several WWE superstars have been called up to the main roster from NXT only to not be booked properly and therefore have either lost all momentum or, much of it. Many of the superstars (Lars Sullivan comes to mind) have experienced exorbitant amounts of success nearly everywhere they have gone, so all the sudden when they are told no or just have difficulty getting over they do not know how to respond because they have never been presented with a situation like this. Many of them have experienced “mental health issues” (such as panic attacks as with Lars Sullivan in 2019).
I believe it’s almost better to have at least some difficulty or adversity in one’s life (particularly early life) and to not necessarily have everything handed to you on a silver platter. Growing up with these circumstances breeds toughness, resilience, and resourcefulness that a person might not develop if they did not grow up in these circumstances. Some challenges in early life are a positive thing because it teaches kids the value of hard work and earning things (rather than entitlement).
Other WWE superstars such as Ricochet, Andrade, Aleister Black as well as Shinsuke Nakamura were former NXT champions and carried the brand before being called to the main roster but have not been nearly as successful since departing. Perhaps these superstars might want to try various nuances to their gimmicks (with approval from the creative team of course). On another note, Triple H is looking to expand the NXT brand and start building a team to operate down in Mexico much like he did in 2018 in the UK.