Can someone explain what just happened in my Matchmaking

Okay so I am not doing very well this season from my own play and the meta shift in ADC in the game atm.

I was d4 56LP last season for my first season of league. https://u.gg/lol/profile/na1/kda%20excalibur/overview?season=12&role=adc&queueType=ranked_solo_5x5

This season I placed p4 and have had a hard time climbing back to diamond currently Plat3 (recently demoted)

I que up for a game on a SUNDAY night at 8:30 PM

I get this guy in my game AUTOFILLED from adc to mid

https://na.op.gg/summoner/userName=Paper+Airplane

He was gold last season and went 1-9 in placements and is currently gold 4 and in my plat2-3 MMR games. (I dodged)

HOW is this possible?????