There is a difference between being dyrus-good and regular good.
A regular good player may play at a skill level higher than their current elo, but aren't good enough to carry his 4 teammates by him/herself, and can possibly get stuck at a lower elo than he/she should be playing at. I was an example of this when I was stuck in the 1200s. I was better than the average 1200 player, but I was unable to carry the rest of my team single-handedly and that resulted in me being stuck there for a month or two.
Players like Dyrus or other pros are capable of carrying their 4 teammates just because they are so far below their actual elo.