I guess they reasoned that building aircraft and equipping and training troops with a system that could not safely deliver a required capability was an even bigger waste.The US Army has already twice canceled potential replacement efforts for the armed scout. In 2004, it terminated the Comanche program after spending $9 billion to produce two prototypes.
Four years later, it canceled the Armed Reconnaissance Helicopter. And now the Future Armed Reconnaissance Aircraft helicopter.
Times and the way of warfare change, but every time totally cancel programs is such a waste of time, money and resources. Its better to put it on hold and adapt the design, to continue later.
My guess in this case they are probably right to cancel (and pursue uncrewed alternatives) - their mistake was leaving it too late but I have no way of knowing when the uncrewed alternatives became viable.
I agree entirely with your broader point in relation to some of their other cancelled (armoured vehicle) programs.