I suspect the strategy was 'we've already saturated the liberals. If we can release a truck and I switch to the other side I can capture the other side of the market as well'.
End result is he has neither side and neither the trucks nor the sedans are selling well!
I don't think Musk or Tesla had a strategy in this regard, Musk was just being impulsive and didn't really think about his brand, I think he isn't really self aware even if he must be smart in some other regard (unless his success is an accident, which I doubt).
I imagine he has fallen in the very common trap of being surrounded by sycophants.
A lot of people have a very strong incentive to attach themselves to wealthy/powerful people, and then try to manipulate their understanding of the world and events to their favor.
End result is he has neither side and neither the trucks nor the sedans are selling well!