Started Rank today; had Plat 5 in my game intentionally losing with his premade. I'm confused now

Can someone explain why they would do that for a lower rank?

The premade wouldn't let myself and the jg FF either. We kept trying to but they wouldn't let us. They premade was a Plat 5 and two Gold 5's. Our JG was Silver 2 and it was my 5th ranked game of promos. So, I have no idea where my rank would be.

The enemy was two Gold 5's and silver 1's.

My friends told me rank sucks now b/c of "dynamic queue". So far of my 5 ranked games I have had two ranked games ruined by premades. So, I'm looking at 40% of my ranked games are being ruined by 3 man parties. Yet, I'm punished for their intentional behavior with losses. It makes no sense.

I don't see the point in having games intentionally ruined 40% of the time. I would be okay with it if I could leave the game w/o punishment but if I do I'm at risk for punishment. You get stuck in games with these people for extra period of time that you could have played another game and moved on. The extra time spent stuck in hostile environment makes me hate playing.

Why do these groups have the power to troll and keep me stuck in the game? It makes me not want to bother with the game anymore. Is it possible to play w/o getting a premade on your team? Why do they have deciding power through votes as well? Shouldn't their group only receive 1 vote?

Should I just quit or does Riot actually follow it's ToS and ban people like this?