Stamina(or lack thereof), defensive IQ, Athleticism/Speed compared to opponent being guarded.
I don’t think the pace would be the direct cause for more fouls per possession. I don’t think the sim goes”oh you’re playing fast, so you automatically foul more”. However indirectly yes, the faster you play, the quicker the players will become fatigued, and fatigued players will be prone to fouling more often due to not being quite as fast or athletic as they would be if they were fresh.
IQ; very important, young teams will be caught out of position and end up fouling more trying to recover. Not sure if the sim accounts for it but I can imagine pace could affect this since the players will be trying to make quicker reads and if they don’t know the system will be more prone to mistakes(illegal screens, etc)