I think Rand decided that the best way to improve on his dad’s success was to cozy up to the right members of the Establishment and play the political game. When he compromised on his principles supporting the likes of McConnell, Ayotte, etc., he lost his dad’s base.
Good post, but I’d also point out that the workings of the U.S. Senate are very different than the House. It’s much easier to be a principled conservative in the House because gerrymandered districts are easier to defend as a candidate. This is how you end up with some of the most conservative House members representing districts in some very “blue” states.
simple answer. Rand does not carry his fathers policies.