Why is the majority of players in bronze/silver, while the player pool for the others smaller?

Currently trying to get into gold when I heard someone mention gold gatekeeper as an insult but it might make sense. I tend to see a lot of sub optimal champions being picked and end up losing lane/game. On the other hand I have seen plenty of streamer pick these same champions while being able to go even or win lane instead of losing. With the main difference between the two I believe are game knowledge, mechanics, and decision making. Which is why I think there seems to be a major difference in player pool between silver and gold. Where champions that are meta are able to start making a difference since players lacking in one or more of those 3 are not able to play around those advantages. Just my theory for the noticeable difference between the silver and gold.