Performance discrepancy between the 2 arena modes

I have a huge discrepancy in winrate in between the 2 arena modes. I am currently an infinite in the regular arena where I landed 5runs with 5 wins each, on the other hands I have a 2.1 avg winrate in underground. I was a bit pissed about my underground performance and I wanted to see if the other arena mode was more generous and in fact I performed better. I am not doing anything different in between my play stile and how I draft in the 2 modes and I don’t understand why this is happening. I don’t have replay on hands but anyone has any guess or thoughts on why I am so bad in underground vs regular. I used to average 4-5 wins and not I can’t even get to 3…