I think you'd be surprised how many votes for Trump in 2016 were actually votes for "not Hillary".
Otherwise yeah you’re right some did do just that for that one time.
However he continues to work with the Trumps. Recently he’s working with Trumps to oust Liz Cheney. His own PACs focuses include many non-libertarian focuses. Immigration control, strict border control, supporting the military as it is now, are some of the top issues of the PAC. These actions are of a conservative Republican, not a libertarian.
None of those things prove he's not a libertarian.
The Liz Cheney stuff was about working with Don Jr. The reason why is unimportant.
The entire point of all this is for there not to be one smoking gun. It’s a collection of everything.
The entire way the right has obfuscated things is by getting by with “no one thing proves I am or am not X or Y”
Political maneuvering doesn't mean someone is not a libertarian, and military and border control are not incompatible with libertarianism either.
Thiel like anybody has pretty complex views that don't fit neatly in a box, you could argue where they put him in the spectrum, but the examples you used are poor. I know many libertarian purists obsess over their image and "principle" to the detriment of actually achieving anything politically, but that doesn't mean all of them act this way.