How am I Diamond 2 in a smurf when I am hard stuck Plat1/Gold 3 in my main?

I have been playing on my D2 account for almost 2 weeks now and I have the same consistency as I do on my main account. Like I get Match MVP’s 2 or 3 out of 5 games on both accounts.

I created the now currently D2 account as a smurf so that I can have some fun and not worry about my main rank and was surprised that I got all the way to D2. Right now I am at 56RR on D2 and yet I am 89RR gold 3 on my main which I have been playing since Beta?

What do you guys think the issue is here?