Is creating new account a bannable offence?

Hello,

I'm a dota player who has a really pretty low MMR whose peak MMR is 2k. Recently I made a recalibration and my MMR decreased even further. I had been gaining my MMR back, but the level of the games were even worse than my 2k games and I don't have enough time to climb.

Probably most of you think that "you belong to your MMR" however I really doesn't take any pleasure by playing with and against the guys that buys 2 boots. Therefore, I thought I can have a new account and make a fresh start.

I played just one game in that account and in the consecutive 3-4 days I didn't have enough time even for logging on the steam. Today, I realized that I got banned from the game. Now I have some simple questions.

Is it bannable to create a new account? If so, how can even pro players have new accounts? If it is considered as smurfing, I'm not a smurf, I'm just trying to play the game at the level that I belong to. Also, what can be the cause of a ban apart from this issue? I use overwolf and I wonder if it has any effect on bans.

Please don't critisize in terms of having new account, I don't ask whether it's logical or not, I just want to know that why my account is banned in a single game. Same thing happened in the last year's calibration as well, and I tried creating new account, this account is banned, I climbed back to my MMR but this time I have really no time. Is it impossible to create new accounts without getting banned?

If a player can have at most one single account per time (which shouldn't be correct because we have lots of opposite examples), then I can close my account and continue with a single new account.

If anyone interested, here is my dotabuff https://www.opendota.com/players/1304678300. I can share additiional information if it is needed.