What would have happened if Zoom had worked fine on their end, but I was randomly unable to connect? Perhaps it would have been fine—they would have been understanding, and we would have rescheduled for another day. Perhaps if they hadn't been understanding, I shouldn't have wanted to work for them anyway.
But, I don't know. I wanted to work for them, and I was competing with other candidates who presumably interviewed on different days. Hiring processes are inherently imperfect, and lots of things can be consciously or unconsciously treated as a red flag.
(And yes, lots of other things could have happened on the day of the interview. But I still find this scenario particularly scary to think about.)