That's a bit odd. They normally don't travel much and go straight in the ground to pupate. I have three in the backyard at the house (countless ones around the pond at the cabin) and I don't think I've ever found one more than 10' from a tree.
I guess maybe they didn't reach a size big enough to pupate and had stripped the tree clean and were looking for food?
These two were planted w/in a feet feet of daddy's shop. And yes, this happened after the leaves were eaten...