It is hard to figure out how to get the engines running in a truck at a moment's notice. How do you know which way to turn the key? It takes a lot of training, certification and high union wages to get someone to do that.
They spent the money on infrastructure. Radios, hazmat training, etc. That truck he bought gets maintained because it gets used. Meanwhile, the trailer it is supposed to haul someday (and if there is an attack, there will be mutual aid and repositioning of these resources to cover any new gaps) could sit there for months with a flat tire, and no one would notice.