So I've thought of something that actually makes sense for why Loki acts so differently in the series. He is having a new kid at school moment. Many of us, myself included, know the feeling when you move to a new school and no one knows you. It's the perfect time to reinvent yourself. There's no one there to say "what in the world are you doing? That's not like you at all." Total freedom.
Loki no longer has to conform to the expectations and rules of the past. He doesn't have to hide his emotions from his manipulative father. He's not around Thor and Thor's friends who would call "magic is cheating. Learn to fight like a man". Not even Frigga saying "no running inside" or "no playing with your food" "that's not princely behavior". The series shows Loki playing around with who he could be, more than who he has been. And that's why there is more similarities to Ragnarok than any other film. That was another time he tried to reinvent himself.
Just kinda my thoughts. Maybe I'm biased because I like seeing playful happy Loki. Mischief is not inheritly a bad thing. It can also be a bit of checky fun.
Also side thought. He just came from New York, where it was heavily implied he was majorly under the influence of Thanos. Seeing that the stones were useless at the TVA, was another moment of freedom for Loki. It meant that Thanos couldn't get to Loki, Loki was safe. If Thanos could have gotten to it, or even known about, the TVA he would have already shown up.
