The bots do not have accurate ratings. It’s pretty typical to be able to beat bots that have a much higher elo than you
Can easly beat 900 bots, but stuck at 500

Low rated bots play perfect for a while, but then make obvious blunders. Most players play consistently throughout the whole game.

I think a lot of it comes down to play style. If I'm playing well and my 3 brain cells are in working order I can usually beat the 1500-1600 rated bot but then I will play a real person of similar rating to myself and they will play in ways I'm not used to or haven't seen much. Throw in time controls and a bit of panic and I'm back to square one in terms of chess knowledge.
Also it's worth noting at the bottom of all the chess bot portraits there is a manual slider you can adjust so you don't have to go from 900 to 1200, but 900 to 1000 instead if you wanted to. Good luck!

... time controls and a bit of panic and I'm back to square one in terms of chess knowledge.
This is me right here, same ^

I beat 1000-1500 bots but have below 300 in blitz. I havent got much time for rapid but I have done better there. My conclusion is that I make huge blunders when I play against others. I do not do these blunders with bots... So why do I these blunders? It's because I do not do the basic check-list and overthink - think too strategically. Especially it is in middle games these things happen. I guess that applies for a lot of others as well: Great openings, big blunders in mid game and ok end-games (if you survive).
I am about 500, and even though I have been playing chess for a while on a board, I am stuck on 500 while I can easily beat 900 bots. I haven't tried 1200 though