What I understood from the PopSci that passes HN every now and then is that the 'Alzheimer protein' is just some normal protein that the brain makes during norm

What I understood from the PopSci that passes HN every now and then is that the 'Alzheimer protein' is just some normal protein that the brain makes during normal operation every day. In your sleep the brain contracts and 'flushes it out' somehow, but over the years the protein accrues and you suffer dementia. Obviously that's super oversimplified and probably wrong, my source being skimmed over PopSci and all. Since dementia is a disease that happens at a late age, there doesn't need to be a reason why it is there. It happens a long time after reproduction, so its effect on evolution is minimal, worse it could even be evolved as a mechanism to curb older specimens in the species.