I guess they thought having a Mum-Ra stand in would seem different enough if they made his non-powerful (less powerful?) form not quite so feeble. Maybe it saved on action figure molds, too.
I've always wondered if he was just yelling the name of his hawk, or if he chose to use the name of his hawk as his battlecry, or if that was just something he liked yelling so he also named his hawk that.
So to do this they had to set off dozens of artificial volcanoes and alter the orbit of an entire planet? Seems like a lot of trouble to go to just to put on a disguise.
This is the only thing I remember about this show, probably because I had a Mon*Star action figure for some reason as a kid. I didn't even realize it was called "Silverhawks" until this came up in the hopper.