I have read that the pyramid was vandalized several times over the years. There was a time capsule inside at one time, which was removed/stolen decades ago. Supposedly it contained nothing particularly important or valuable (time capsules seldom do). I visited the site a few weeks ago. It's a shame it is gone, but at least they replaced the name markers of the individuals whose names were carved on the pyramid.
edited to add:
https://www.jehovahs-witness.com/topic/5097906067996672/visited-russell-gravesite-yesterday