What do Valve gain on, when they rigging the MM?

I don't really care if anyone of you telling me now something like:
"Uh you're just bad and you deserve to be in 2k forever since you can't get out of it".
That's not the case here.
THE RANKED MATCHMAKING IS RIGGED. PERIOD.
Let me put it this way:

I had 8 wins in a row, and I play good.
Most of them are MID games, with Invoker and other significant heroes.
After the win streak games, I lost 1 game with OD, and I quitted and didn't play for 2 days cause I knew if I keep on playing, I will just keep on losing.
Coming back 2 days later (Today 2022 / 01 / 26 ) and guess what?
The losing streak is on.
Valve will match you with people that are completly braindead, and toxic, and that will not contribute to the game at all, cause by some reason they WANT everyone to be at 50% winrate and 50% lose rate, sometimes even more lose rate.
Why is it like this?
I've been thinking about it:
Why do they put in Smurfs in these first 4-6 losing games, that they KNOW you won't win against?
I can't rly think about any decent reason, but why the fuck do they have a report function for it when they clearly are planting losses for you?
I'm so tired of this shit. 2 YEARS ago I was almost 3k, without a PROBLEM, now it's impossible to win against people cause Valve will RIGG the matchmaking.

If anyone sits on information on WHY they do this, please explain it for me, because I don't believe that they ain't doing this shit.