The crevice in D11 is in the top 5 of the the most epic base locations in the Exiled Lands. It is the largest cave to build in and therefore has immense defensive capabilities. It´s location is a dream, and on top of that, if you build it right, because of the huge mountain, you will gain supreme strategic control over a huge area. Of course, people fight for this location, and as you built inside, someone else wants to do it. So, claiming this spot after deleting your structure is only part of the legit and epic war this game is so great in simulating.
I don´t know about the rest, because you only made some hints regarding the amount of other building locations that they claimed, but in general land claim on a PvP server is regarded as a part of the warfare. You can read yourself about what funcom defines legit or illegit in the guidelines about official servers from April - here´s a part of that:
I read the last sentence as: “On PvP-servers, where people can clean up themselves, it is less likely that funcom will see the necessity to intervene”.