Because they're never fucking satisfied by what they've actually voted for. It's essentially the fundamentalist dynamic of blind faith, applied to the real world and making for terrible results.
The con artists they vote for are plainly not going to help their interests (and often work against them), yet they reject understanding this and instead buy into simplistic emotional propaganda that validates their frustrations and absolves their responsibility. Then after some years go by when the mess has set in and Democrats have the nominal power, the Republican media machine goes to work highlighting everything they've broken and pinning it on the current administration. Rinse and repeat.
(context: I'm a libertarian and I have many criticisms of the Democrats as well, but at least they haven't been directly sabotaging the country for the past several decades, culminating in this)
The con artists they vote for are plainly not going to help their interests (and often work against them), yet they reject understanding this and instead buy into simplistic emotional propaganda that validates their frustrations and absolves their responsibility. Then after some years go by when the mess has set in and Democrats have the nominal power, the Republican media machine goes to work highlighting everything they've broken and pinning it on the current administration. Rinse and repeat.
(context: I'm a libertarian and I have many criticisms of the Democrats as well, but at least they haven't been directly sabotaging the country for the past several decades, culminating in this)