If you abandon your stuff in somebody else's yard, they own it.If you build something on someone else's property without their permission, who owns it?
But it's not a reasonable thing to do with military gear. Normally, you'd take it with you when you left. In this case, there was no time - Trump made sure of that.
Or keep any of our promises, or cultivate allies, or anything of the kind. Because who needs friends or diplomacy when they have the Marines, right?We have no need to control the region.