Why are plat people so cocky?

So I'm gold 5 right now, which isn't very good and certainly isn't where I want to be, but I'm above average, which I believe is silver 4 or 5. And I constantly play with platinum people (low plat) that are really cocky and toxic. And it makes me wonder: why?? Low plat is NOT good at all. I've seen plat 4 people that play like fucking wood 6. It's considered low elo by diamond and higher people. And whenever I make a mistake, they say "oh no wonder, you're gold". That's like a silver 5 person thinking they're good because they aren't bronze anymore. It just makes no sense because the majority of low plat people I've seen are cocky fuckers. And I'm not just saying that because it's a stereotype or anything, it's really, honestly, true. Of course, if you're in plat, you're higher elo than average. But it doesn't mean you're good. The majority of low plat people are one tricks because they aren't actually good enough to get to higher plat. I can admit that I suck; why can't you?