Humans differing chromosome count

Goat wrote:

Another one was the prediction that when it was discovered that the humans had one chromosome pair less than the other great apes, there would be a fusion event discovered, and that fusion event was found.

OK, let’s explore this.

Chimps, Gorillas, and Orangutans have 48 chromosomes (24 pairs). Humans have 46 chromosomes (23 pairs). If humans evolved, then the fusion event must have happened at the chimp/human split or after the split. Let’s take the first case – at the chimp/human split. When the split occurred, an individual underwent a chromosome fusion by random chance and reduced the count from 48 to 46. But, in order to pass this on, it would have to mate with the opposite gender that underwent the exact same fusion. So the first two male and female humans would’ve both had the fusion at the same time. So, for three events to happen concurrently – first pair of humans to arrive, a male chromosome fusion, a female choromosome fusion – would be quite improbable.

What would be more probable is that the fusion occurred after the split. There would be many humans with 48 chromosomes. So, the only thing that would be required is a male chromosome fusion and a female chromosome fusion and that they would have to mate. Since it’s impossible for them to determine their chromosome count, it would have to be by pure random chance that they would meet. Then one would have to explain why all the humans with 48 chromosomes became extinct. All the great apes survived for millions of years with 48 chromosomes. If they also experienced fusion while they existed, the 46 count became extinct. So, why for humans would the 48 count become extinct?