Do you know much about demo? Personally I have a bit of experience. There was never any footage captured of anyone placing a shaped charge on the guidestones so I'm leas to believe it was hit with something like an NLAW or better yet an AT4. They are insanely hard to get off base though. The only way those stones would pop like that is if someone drilled a hole into the stone and either put some dynamite. Just placing C4 or even C1 on the flat exterior it would just blow off to the side with basically zero impact. Also a fuck ton of Tannerite could do it but once again someone would have to sneak all the way up there with numerous 5 gallon buckets. Which didn't happen. So something with a concentrated jet would be required to cut through granite like that without just deflecting off.
Have you worked much with granite? I've done a lot of drilling and working with it. I've watched that footage a bunch of times and still conclude the most likely cause of that explosion was a shoulder held AT. the way the rocks blow apart it looks like something with immense velocity hit it, as the large chunks of granite have a more uniform direction of travel. When you drill and place dynamite, it explodes in all directions uniformly to a relative extent. It wouldn't heave the majority of it in one direction like something faster just hit it (like an AT forms a concentrated jet)
Long story short it looked professional to me, MIL grade possibly but not amateurs. Definitely not amateurs.