#3 is because rats don't get Alzheimer's.

So all of our models are pretty artificial. And we build our rat models off of our disease assumptions, like injecting rats with beta amyloid because we assume that's the primay cause of brain dysfunction.

But it's looking more and more like that's wrong and beta amyloid is not the central player in Alzheimer's but just one of many. With Tau/insulin resistance/herpes/glial dysfunction/neuroinflammation playing important rules as well.