The reasoning for why 65+ are either Red or Blue seem super obvious to me.
Cohort 1: Dependent on social security, Medicare, entitlement programs and have minimal retirement savings. This group is super sensitive to suggestions that their programs are being defunded and literal livelihood may get taken away. It's easy to see how they might be swayed by dem talking points.
Cohort 2: Collect social security because "hey, why not?", use Medicare but can afford private health coverage if needed, have a nice retirement nest egg set aside from 40 years of saving/investing in a bull market. Their biggest concern is likely around how to maximize tax reduction strategies related to RMDs and withdrawals from retirement accounts. This group likely leans fiscally conservative and votes with their pocket book.
“There is no red.
There is no blue.
There is the state.
And there is you.”
“As government expands, Liberty contracts” - R. Reagan