Kelly and Pete have it right. Humans can be very territorial. Especially cavers, dry cavers as well as divers.
Certainly there is never any justification for vandalizing equipment or compromising someone's safety.
But look at it from another side. Say you've spent months (or years!) ridgewalking, studying maps and geological and hydrological data, working with landowners, lugging equipment through the woods, donating blood to the mosquitoes, and crawling, diving, and maybe digging in every pothole in three counties. Then when you finally discover going cave, somebody can't keep their mouth shut. The next time you show up at the cave that you discovered and are exploring, there are other people there scooping your find.
Then imagine that this other group, maybe better funded, better connected, or just more politically devious, goes to work with the landowner, the water district, state and federal agencies, etc., telling everyone that you and your team are a bunch of ignorant, poorly trained, unsafe local yokels who are going to end up getting somebody killed, and that they are the only ones who can safely explore this cave. Then you're notified that you no longer have permission to access the cave you found. Access has become permit-only, there is only one permit open at a time, and the other group has it.
As I say, there is never any justification for doing anything that would compromise someone's safety. But humans being what they are, it's not surprising that friendships have ended and that in some cases stupid and/or criminal things have been done.
Mike