Sassafras rot resistance

I had a couple of sassafras that had been dead for 5-7 years before the power company came through and cleaned the lines and dropped the trees. They were already getting torn up by woodpeckers and some rot, so I tossed the limbs off to the side and only planned to keep the trunks.
Fast forward 2 years and I was cutting the limbs to size for the burn pile, I was surprised at how good most of the wood was. The sapwood was punk, but after maybe 1/4-1/2" the rest was completely solid. I decided to split a bunch and will mix into the regular stacks.
I have heard on here and read that sassy is pretty rot resistant, but I have not heard why. Most wood that is resistant usually has a tight grain and is heavy. But this and cedar are neither.

Is there something chemical with it?

Here are some of the splits and a piece of the trunk cutoff.