How can a gold 4 player in solo q, with a teammate that is platinum and 2 others that are both unranked lvl 30 and estimated about bronze in skill based on the gameplay, be matched against a 5 plat 2/3 players that are all a rank which only 1 of our players are?

I know true MMR is different, but since 2 accs on our team were literally brand new iron accounts that were probably on promos this whole premise doesnt make sense. You cant put plats/emeralds against irons/bronzes , especially 5 of them.

Can someone enlighten me how this whole matchmake was possible? 5 plats vs 1?