What happens to XCP when one creates an asset?

So I wonder what is happening to the XCP I spend when creating an asset? Are these burned or used as miners fee, or paid in dividends?

Also who is running the XCP network. Since it runs on top of bitcoin, does that mean the regular bitcoin miners are writing the XCP ledger insider the BTC ledger?

Are the XCP kinda like a miners fee when when we create assets, if so who gets them?

Why can’t we not create assets with BTC?