why plat players act like their bronze/silver

yesterday I played Yasuo Mid in normal. I won my lane. At 15 min our bot just came mid. I don't think its the best time to team, so i told them to go away. Maybe its because they lost their lane too hard. Ashe just kept stealing my cs and xp. Note that they didn't get the bot turret, so theres literally no reason for them to be at mid. They won't leave, hence i went bot farming instead. When I was taking down the bot turret, my team just picked up a 4v5 fight near baron pit. No doubt they lost that fight, but i got two turrets bot. And then everyone started flaming me. "nice team fight yasuo". By the time I'm lvl 18, my team were around 12 and 13. Our top is plat v. Unlike our bot at least He had a decent farm, But in mid game he just starts picking 1v4 and 1v5 fights. Whenever he died from he's own decision, just like other bronzies he immediately starts raging me for not fighting(dying) with him. Im only silver 5, I know I'm not good at all, but i'm sure those guys in my team had no idea about this game. All they do is flame and being toxic when they died of their own mistakes. It really annoys people, and ruins the game. Thank god it wasn't a ranked.