Yes, it has to do with a lot of things. One is b/c ppl are cursed when they move up

(jk obv). But seriously, it can be b/c the plrs are better/ play different, adjustments need to be made, more money is affecting your thought process, different bet sizes (probably not at sngs). Any of these things can be a factor and probably some that i'm forgetting.
Also, it can just be standard variance, you run/play good for a while and then when it's time to move up you just aren't running as good anymore. Then one thing leads to another and boom! downswing. I often downswing when i move up b/c when i lose 4 BI"s at that limit i think "oh shit, i just lost 8 BI's" and stuff like that just messes w/ my head, and it leads to tilt and so on.