There's an interesting article on fivethirtyeight.com about offense in the bubble and fouls in the bubble. Fouls are up in general across the board. I wonder why this is. Do you think it's easier to see fouls/hear fouls without fans in the building making a ton of noise? This whole article is fascinating actually. https://fivethirtyeight.com/features/why-have-nba-offenses-been-so-good-in-the-bubble/
Probably there are multiple factors involved, would be my guess. Rusty players commit more fouls, but I wonder if being able to hear more clearly has an impact. Where sounds of hands slapping flesh on a reach-in might be covered up by crowd noise, they would be a lot easier to hear in the bubble situation. The psychology of not wanting to bog down games where there are 20K fans booing you could also be a difference.
I think the lack of crowd noise is the biggest factor, by far. You can hear everything now, including coaches and players screaming for calls.