How is it possible for two black holes to collide?
From my understanding, an observer witnessing an object fall into a black hole will never see it cross the event horizon; the falling object appears to freeze in place because of time dilation. In the process, the falling object redshifts and fades away from sight, but as far as I know it never actually crosses the event horizon threshold.
I also know that we have evidence of and have even detected black hole collisions. I'm not sure if we have any other detected instances of objects falling into black holes.
Why do black hole collisions not result in them freezing in place (from our perspective) right next to each other?
I found an old post on this sub with a similar question but not exactly the same: https://www.reddit.com/r/Astronomy/s/Z8wxmcF4bZ.
Edit: There might be some confusion, maybe from my understanding or the wording of the question. I'm not talking about what we literally see with our eyes.
I'm talking about how time appears to slow down for the falling object due to general relativity. Because of that, it eventually reaches a point where it appears to us that no time passes for the object at all. Since time for the object appears to stop for us, the object never crosses the horizon from our perspective (because it takes an infinite or close to infinite amount of time to happen).