Why are there cabal and fallen at the tower?

I was a die hard destiny 1 vet and I stopped playing destiny 2 after the year one season pass ended because I just didn't like the direction the game was going and I saw the writings on the wall with Bungie constantly screwing up the game.

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But since I started playing again, why are there cabal and fallen at the tower, like what the hell happened to the story and all the characters. It just feels like all the characters are so annoying and whack.

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But even though I really do not like how the characters are and whatever happened to the story. it does feel good to be home again I really missed playing destiny so much. I never wanted to stop playing I just got tired of bungie's bullshit.