Explain this to me- 2 acounts diferent elo

So i got an interesting predicament. I decided to get Plat on my smurf account just to see if i was decent to do so, started in gold III on placement games and got to plat 5 in around 50ish and 70% w/r games , anyways i got it by essentially one-tricking Malzahar, and by the end of it i was facing plat 3 -2 because i got such a high w/R that mmr skyrocket.

Fastfoward 2 days and currently i'm on my main account, which has gold 4 mmr and i can't win more games than i loose, while playing the same champs. I just get teams that are just amazingly bad.

So i'm just wondering has anyone else experienced this. I mean the exact same context but in different accounts i get vastly different results.