This proposed parade has nothing to do with honoring the military. They are just the pretext for the parade. The real point of the parade is to try and pump Trumps popularity ratings by cynically appealing to peoples since of patriotism.
If it were really about honoring the military, Trump would come up with something much more substantial and permanent than a parade. Maybe he's just ashamed of himself for being a 5 time draft dodger and trying to get some sense of forgiveness for putting his money where his civic duty should have been.