If the guy playing Biden is a guy in a mask why doesn't he act normal and intelligent??

It's believable

To slant the world view by those creating the pole flip that old people are a nuicence that needs to be put down.
Euthenasia of the elderly propaganda.subtle isnt it?

Because there is an expectation of consistency.

However, the guy in the mask over acts sometimes to have fun with his role as the senile president. Probably also to demoralize the public.