The main problem is sweat players that don't realise they are playing a casual game like Battlefield. It's a 32v32 game so it's literally impossible to have a proper matchmaking with Battlefield's player count, finding 64 people with similar skill would lead to queues of at least half an hour, forget about server browser

Another point is that leaving the game while it's still playing doesn't penalise you, you don't need to wait a second to find another server, plus if you leave while losing it doesn't even count as a lose for you. So people on the losing side keep leaving and it's a vicious circle where the sweats in one team stay and the stomped people on the other team keep rotating. People who are boring enough to stack in a game like Battlefield or to only stick to the meta (ZK-383 sweatlords) don't get bored of stomping a bunch of noobs and winning match after match in under 10 minutes each

These people are probably ranked silver in competitive FPS games like Valorant or CSGO, so they come to stomp in Battlefield. It's similar to griefers in MMO games, they suck at real games so they go there to bully players that just play less hours than them