I was S3 86 and went to G2 17 FROM ONE GAME?!?! like wtf, ayy but at least it made up for me losing G2 in my placements. How does this even happen? Is my mmr just crazy high and reached a certain thresold that it boosted me a rank?

Here's a vid, my reaction to it happening is at the very end: https://www.youtube.com/watch?v=ldQjMCJ2izU