The ranking system has always been kind of a mystery to people, some thinking its about wins/losses, others thinking it's about medals/individual accolades, but recently the Season 8 patch has made Winning matches more of the focus in higher ranks. Their reasoning is those who make the necessary switch and help the team should be rewarded more than the dps who got gold in elims and damage but never helped take the point and ended up losing.

As to why you are ranked the way you are, even though you lost your placements, you lost to GMs and Top 500s, which is better than losing to Diamonds, Golds, Silvers. You at least held your own. They need more transparency as to why ranking works the way it does in my opinion.