These placements make absolutely zero sense. Please explain what just happened to me...

Please someone explain this. i literally got screwed out of my rank like... what... im speachless on how this just happened. I ended season with gold 1 rank. My MMR was really high, playing plat 5-3's constantly. I was on a 10 win streak, including 6 wins ending last season, and 4-0 in placements. I got two unlucky disconnect team mate games. I ended 6-4 in placements. When I asked people what their last seasons ranks were in a few games, i mostly heard they were plat. HOW DID I GO DOWN IN RANK??? How do I go 6-4, A POSITIVE WIN/LOSS RATIO, playing at higher then gold MMR, end last season at gold 1, AND GO DOWN IN RANK? WHAT!? Please someone explain this. Please... im begging how this math even adds up.

EDIT: I PLACED IN GOLD 5. 4 DIVISIONS LOWER THEN MY END SEASON RANK.