What's going on with this season !?!?!

It goes by your MMR last season. Then it drops it a bit. Placements are pretty much useless because it doesn't matter how well you do, you're rank is going to be your MMR - some number. It's why a lot of people bitch, and it's pretty wide known. Unless you're a fresh 30 account, placements don't matter.

preseason games can also determine your mmr

QT was challenger rank 1 and he placed in plat. how do you think that feels lol.

Nothing. Placement games are to inform your placement. It is not "X out of 10 = Y rank"

You would have definitely been playing against low Bronze and you can't expect being placed in high elo for winning a handful of games against them.

if you went 10-0 you still would've got bronze 3... you were bronze 4 last season why do you think it would start you higher rank than you were last season? i was D5 went 7-3 and i got P2