How the hell can be such a skill difference between same division players?

This is not qq post about how I can't get out of lower divisions, becouse I have no problems with climbing at all, I just want to know something. How the hell skill difference can be so huge between one gold player and another one?

I was p5 in preseason. I got placed in g5.

In one game 4 of 5 oponents played like bronze 5 players, going 1vs3, not trading with enemie while in laning phase, etc. My whole team was comunicating and listenening to the calls.

The other game my 3 team mates were blaming everyone, proccesed to go 1vs1, 1vs2 or 1vs3, flashing in to 5 enemies to finish support, while having half of CS enemie had, no one listened to the calls nor looked at the map.

Another game, we had insane lead, but our team comp was very bad and I said from the begining that we have no chance late game and we must rush baron to end the game as early as possible. We aced enemie team, I pinged and ran to the baron, while everyone were recalling with full hp... -.-' Enemie took baron and we lost....

Edited: same things were happeneing in platinum, but at much lower frequency , it seemed that some people had no clue how the game works and it's not becouse they were bad with certain champion, but everything they were doing was bad, not looking at map, ignoring pings, trying to roam while losing 20 cs, etc....