Yep, Brian, that, plus the old top breakout, was likely the start of problems with this tree. Otherwise, with it's location near a stream, and having had no major construction within 15 feet of the trunk, it would likely have been in great shape.
Bigleaf maple is the largest maple species in the world; there are specimens over 150 -160 feet tall, and 11 feet in diameter.
In relation to the old cuts, few trees can handle 24 inch cuts, flush or not. Bigleaf are notoriously poor compartmentalizers.