IIRC, all their campaign infrastructure was like that.
The Paul campaign was the only one that actually prepared for the primaries start to finish. And had a general election budget strategy, even if unlikely to ever be used.
Everyone else was assuming they could buy a campaign up later, which was how it traditionally worked. (Though 1996 and 2004 should have really made it clear that's not the case anymore against an incumbent.)
Santorum and Gingrich's campaigns didn't even remember to file to get on the ballot in a bunch of states, Gingrich most of all, there wasn't even really any campaign except for his showing up at debates and whatever Sheldon Adelson was throwing money away on.