I know you're getting downvoted a lot, but I don't think you're a Trump supporter or arguing in bad faith. I know what you mean.

People on the left, like myself, were always going to call the parade a failure. It was always going to be a sad, pointless attempt at spectacle. By its very nature, it was a failure. In no world were we going to say, "yeah I hate the guy, but damn if he doesn't know how to throw a bitchin' parade."

On the flipside, Trump and Maga folks were always going to call it a success. Or maybe there are reports of angry red hat people who expected a better show and were disappointed. Unlikely, though.

On what terms do you define its success or failure? Yes, attendance is one. If they expected ten times as many people, then, as you say, it's a failure. You aren't wrong for asking for a source.

I think your original comment was less along the lines of, "how do we know it wasn't an amazing success, though?" and more like, "wasn't the parade exactly as expected?"