Wow! That's quite a sycamore!
Even without a foggy, misty day a less-than-experienced person on the lowering rope can add a lot of stress when working down a large tree in a tight space. That is a great photo. Wesspur material for sure.
Yesterday morning had an oak and honey locust prune and in the afternoon finally got some free time to get the bucket over to an interesting sweet gum removal. It had been dropping 4" to 8" limbs, sounding showed a hollow at the base that ran about five feet up the bole, and it was time to get it out of there.
I had started up it a while ago, limbing as I went, intending to lower it out, with wires and a sycamore next to it. At 35 feet up there was a squirrel hole, and my hand saw wouldn't reach the other side. Cut myself off a small probing stick, and there was only about 3/4" to 1" of good wood all around at the main juncture of all the leaders! The entire top was on a hollow tube. No lowering out with me in it; not worth the risk of it failing.
The area used to be low, swampy land, which was used as the city dump back in the 1930s to 1040s. The builders brought thousands of tons of fill in and raised the ground level about three to five feet. When I was young the older trees all had brick walled 'wells' around them, each about three to five feet deep. Made great 'forts' for snowball fights. It's amazing to me that as many of those trees survived as did. This tree went pretty much straight into the ground, with very little root flare. It was only 28" DBH, but was there when the house was built in 1966!
Got it down, and the hollow in the trunk extended about five feet down (eight feet if you count the section of stump I left), and a good foot and a half below grade are two tree rods holding the split trunk together. We'll be able to grind the stump 15" below grade and not hit them!