HCA: Hermit Crab Association

Hello! I am a new user here and am relatively new to crab keeping (I currently have 2 crabs in a 10 gal.). Six weeks ago I had a crab go down to molt, and it hadn't come up yet. Just yesterday, I was moving around decorations and I poked a hole in the substrate with one of my little logs and it sunk in several inches. I thought that it was probably some tunnel the molter made and I decided it was best if I didn't mess it up anymore. I ended up putting a pineapple decoration on top of it so that the other crab wouldn't end up bothering the molter.

When I came to the tank today I saw the non-molting crab had dug underneath the decoration (where I had poked the hole) and began digging itself into the substrate (it hadn't dug deep enough yet so it was still nearly at the surface but it had essentially made the hole that I made bigger). After a few minutes I noticed that it began going back into its shell; it had removed itself from its shell after it had dug down. Not only that, I noticed that the molter was right underneath him, looking well and all (but still out of its shell).

So I have a few questions:
Why did my non-molting crab dig down there all of a sudden (at that very spot)?
Was my non-molting crab trying to molt? Did I disturb it?
Why did my non-molting crab choose to dig down to be right on top of my molter?

Thanks a lot for the help in advance! I'm eager to read of what knowledge you guys would have on this.

*something to note: I put my 2nd crab into the tank while my 1st was molting so it never knew there was a previous crab in the tank (it at least had never seen it)

How deep is your substrate? It should be a minimum of 6 inches or 3 times the height of your largest crab. Whichever is deeper. Crabs dig all over. They tunnel from one end to the other so there's really no telling where they really are. If your substrate isn't deep enough they will run into each other and if molting that is a problem. But crabs should never be shelless. If a crab is out of its shell it has to be reshelled immediately.

My substrate is at exactly 6 inches, and the non-molter re-shelled itself immediately after being exposed to the light. I've been monitoring my non-molting crab's behavior and it seems incredibly interested in the molter. Twice I have gently placed it on the opposite side of the tank only it have it scurry back to its old position near the molter. I've decided that I probably shouldn't be bothering it anymore but I'm not sure why it's so interested in the molter now, all of a sudden.