I didn't downvote you, however I think people may dislike the idea of one having their own pet hypothesis without linking serious evidence to back it up. Amyloid plaques have been heavily studied and may have some tangential but real link to Alzheimer's, it's a plaquey protein found in the brain along with Beta-Tau which is another protein I believe. I personally haven't heard of any fungi theory yet, the main ones I've heard were viral things, pollution, or perhaps some breakdown in the brain's ability to clean itself up over time. And why are certain individuals spared and not others? I know there are genes that predispose one to it, and there are early-onset cases which come on more often than others.

If it was anything obvious in the environment, I'd hope we'd know by now...but it may be something hard to measure in large epidemiological studies like a more rare pollutant or something we overlooked in creating large observational datasets?

Anyway, I'd encourage you to link the best studies you've found and that may help some to read them.