Judging from the picture of the remnant, the maintenance of this particular pyramid had been left to the jungle for some time but when you're talking about a large stone or stone covered gravel structure a good thick covering of dirt and vegetation will preserve it nicely against everything except, it seems, large excavators and such.
Many archaeological digs are simply covered back over with sand or dirt to preserve them form the simple elements. In this case, though, something other than the simple elements came along and did the damage.
Now, if you're going to uncover them and try to keep them in a pristine state while tourists climb all over them (which others have commented was not happening here.) then I can see where there would be a taxpayer burden.
I still expect that the full truth will be that the landowner saw a good opportunity to make some money selling some easily accessed gravel and fill and told someone to have at it. No one has mentioned yet who paid whom for the gravel and the equipment to move it.