Its simply two sets of variables, one set I cannot do anything about or affect in any way. Another set is entirely up to my choices/inputs as to what those variables end up as.
I can make every correct/best decision I possibly can and the other set of variables can still give me all tails in terms of coin flips that match. Great example was when I played as the gambler hero, I finished as 2nd place playing the composition I did, but every single time I used my hero power and had to pick who i thought would win the next matchup, I got a big goose egg every time. I cant affect how that matchup actually goes, and the odds arent great that the entire match I would NEVER get a single one correct despite the evidence I based my picks on such as their unbroken win streaks until I picked them for my hero power wager lol. Pure coin flip 50/50 odds every time and its possible to just get tails every time despite it not being a super common thing. But I still took 2nd place despite it lol.
I dont cry rigged or say mmr this or that. Some things I can control, most things I cant. simple as that.