Stop apologising for life happening.

I can't help it, I'm part Canadian. 😅

So I get being concerned about friends and all but why was Mullet missiling down a pitch black cave XD

So, the short answer is, its just the way he is.

The long answer... part of it was the growing "I'm indestructible" aspect of the character. Part of it is his survivors guilt caused by not being there to save his family. Mostly Mullet is stupidly loyal to his friends and will always rush headlong into danger for the sake of others.