Promotions Match making

Come on there has to be something different riot does. It is not coincidence that every player seems to get worse teammates in promos. There will be people who deny this, but it is simply fact at this point. 1 ranking doesn't change my average 10/2 carry to impossible to win games. I think they either pick the people who aren't climbing and the ones who fail their series the most. This seems to make less sense as if u can possibly carry the ultimate garbage, they get put in ranks they aren't supposed to be.

First tell me what riot does differently in promotions match making, and it is different, then maybe ill figure out how to carry them.