Why does my rabbit keep pull up his flooring

My rabbit is I think about 3.5? Months old​​? Havent gotten him neutered yet but working on it.

I used to have rugs on my floor that he never messed with when he was free roam, but now that he had a 'pen'/enclosure, we have towels and one like mat thing? we used to have carpet down but he kept pulling it up. he keeps moving the towels to lay on the floor for some reason though. I don't know why he doing it and I can tell he's struggling to walk around when he does.

The only reason I could think he does it is he doesn't like how it feels or because the floor is colder? (I've had my heater on a lot recently bc I'm hypersensitive to temparure, mostly the cold)

Towels are also temporary. It was the best thing we had sense the rugs got pretty dirty and were small