Placement matches?
I won 6 out of 10 placement matches this may not be the greatest but was placed in B5 when i ended last season B2 what happened?

I won 6 out of 10 placement matches this may not be the greatest but was placed in B5 when i ended last season B2 what happened?

Well that doesn't seem fair.
Most people were dropped around 3 divisions worth of MMR this season. The only way to break even was to have a very good MMR for your division, and do well in your Placement matches (most importantly, the first several matches since apparently they are done in order of MMR highest to lowest).
Going down didn't mean you were screwed or you suck. You'll just have to work back up since you're in exactly the same position as everyone else.