Why are they doing this? Because they can.
Jamelle Bouie answers the question as to why the Republicans are going forward with their kill people for tax cuts bill despite the fact that it's the most unpopular piece of legislation in history:
The 2018 House map still favors Republicans, and the party is defending far fewer Senate seats than Democrats. Aggressively gerrymandered districts provide another layer of defense, as does voter suppression, and the avalanche of spending from outside groups. Americans might be hurt and outraged by the effects of the AHCA, but those barriers blunt the electoral impact.
The grounds for political combat seem to have changed as well. If recent special elections are any indication—where GOP candidates refused to comment on signature GOP policies—extreme polarization means Republicans can mobilize supporters without being forced to talk about or account for their actual actions. Identity, for many voters, matters more than their pocketbooks. Republicans simply need to signal their disdain—even hatred—for their opponents, political or otherwise. Why worry about the consequences of your policies when you can preclude defeat by changing the ground rules of elections, spending vast sums, and stoking cultural resentment?
It seems, then, that we have an answer for Republicans insist on moving forward with the American Health Care Act. Because they can. And who is going to stop them?
It appears they also have a foreign country helping them get elected, for which they seem to be very grateful.
They don't fear the voters because they have managed to create an alternate universe for them in which everything bad that happens to them is the fault of hippies, feminazis, immigrants and people of color and everything good that happens is because of them. When liberals scream they laugh with delight because it means we are seeing justice at their hands.
And they've successfully created an electoral system than keeps them in the majority through undemocratic means. It's a sweet scam. No wonder they are so confident. They have staged a silent coup and we just have to live with it.