Republicans stopped being libertarian when they started supporting Trump.

Republicans were a coalition of anticommunists. This resulted in neoconservatives, paleoconservatives, and libertarians coming together. When the Soviet Union fell the coalition started to fall apart leading to fewer libertarians supporting the Republican party since the threat was less. The neoconservatives and paleoconservatives remained in the Republican party.

Republicans were never libertarian in any meaningful sense. There's a reason libertarians have their own party.

You're right. I should have said, Republicans stopped pretending to support libertarian values when they started supporting Trump. At least they used to pretend they were for libertarian values.

The reasons libertarians have their own party is so they can be blamed for in effect voting for Trump when they did not vote for Trump. It is a form of self-flagellation to ensure no matter which sides when, it is your fault to the other side.

When confronted with the possibility of a second term of Trump's uniquely destructive anti-leadership and proven track record of being highly corrosive to individual liberty, if you couldn't swallow your pride and vote actually-conservative then that's on you. I myself had never voted for a major party candidate in a national election. That changed in 2020.