I bought a fan to mount in my garage l. Clearly it's drywall. Weighs about 20 lb..

I drilled the holes and I wanted to use the expansion screws that it came with.

Mounted it okay and tightened it as much as I could. To tighten the nut I had to hold the bolt with pliers to prevent it from spinning at the end. I'm not sure how else to hold the bolt still to tighten it more, if that's even possible.

As soon as I put the fan in the mount pulled away from the wall.

I took everything down but as you can see the expansion screws did its job and it is expanded behind the drywall.

I'm not sure what to do. If I pull it out it's going to leave huge holes in the drywall. But other than that I don't know how to make them tighter if that's even possible.

I have a photo but I can't post here for whatever reason.