That is a myth. The founders were closer to Libertarian ideas than Conservative ones. Libertarians are classical liberals, as the founders were. They were not conservatives. Labels have morphed, and the libertarian principles have been diluted and warped some over time but that is a fact.
I do not believe Big L libertarian's are classical liberals which I guess I would agree our Founding Father were (which is what is currently called Conservative philosophy). Our founding father's, for example, did not ascribe to isolation/non-interventionism or open borders.
As this could be a conversation, I welcome your input but it's a big topic and is hard to go through carefully with just a casual exchange.
Freegards