Why is 3v3 easier to climb in ranked play?

After playing both 3v3 and 5v5 ranked, I have noticed that I am able to climb a lot faster in 3v3 ranked than in 5v5 ranked and even 5v5 flex. I understand that fewer people play 3v3, but the people who do theoretically play a lot of 3v3, whereas I started my first 3v3 game as normal, and have only played ranked since that 1st game. How fast did everyone else climb in 3v3? I plan to reach plat this season and see it as very realistic. my top goal that I feel I can reach if I stay at this win rate and continue to carry every game is around diamond 5... I won't make any claims till I reach it though. thoughts please?