I look at it this way...think about what it takes to make it as an actor, actress or musician. You're told while you're coming up that it's a long shot and most likely you'll struggle forever. Then as you move up you're told you're not good enough. So the only way anybody to make it through being constantly told it won't happen is to build such a confidence in yourself that it becomes almost an arrogance (i.e. Kanye). Then when you finally make it after years of being shytted on, you get these ppl who used to say you ain't shyt, grovel at your feet to compensate. Feeding their now inflated ego. Some can take a step back assess themselves and some can't...which leads to the "arrogance" you're talking about with ppl in Hollywood.
Also, sometimes these ppl don't want you running up on them calling them out of their name and shyt...I imagine at first its cool but then it grows tired. They maybe having a bad day, w/e the reason...and I noticed some feel like celebrities owe them b/c they saw their movie...they don't owe you shyt. They acted (serving you), you bought it, that's the end of the exchange. They don't owe you live impersonations or even a convo. Not saying that's the case with the TS, but it happens.