Do people ever pass case interviews out of luck?

I'm horrible at case interviews. I got rejected from a few first rounds, but I passed one at a boutique firm recently. So am I not as bad at cases as I thought or did I indeed just get lucky? The case with the boutique didn't seem to go that well either - while I had the right approach, I took too long and had to be reminded of market share twice. Moreover, my camera wasn't working.