In the video, you’ll see a memory test where subjects were asked to recall a sequence of numbers that they could look at for however long they wanted. Ayumu the chimp could do this successfully more than 90% of the time, much better than people.
Chimps “are better at doing chimp things” than we are. Chimps in this case were clearly better than humans at recalling the numbers and this probably means that, for their lifestyle, short-term memory is really important. At this I’m just making an educated guess but I’d say a chimp’s ability to recall exactly an image of something it has recently seen probably reflects the need of chimps to watch for predators. If you are scanning around the jungle looking for a leopard, it will really help to remember exactly what the scene looked like moments before so you’ll be able to pick out the differences (which might be threats) much faster. This would provide a ‘selection pressure’ in favour of chimps that could more quickly identify threats and thus increase their survival vs. chimps that were not so good.
For humans, this short-term memory is obviously not as crucial and this is probably to do with the fact that we mostly have little need to constantly check our surroundings for threats. Human brains have perhaps adapted more towards favouring the long-term memory, though some people do have eidetic memories and can remember virtually everything they see and in great detail