Take off the goodies and torch the trucks. I bet being work trucks the keys were easy to find, if not already in the ignitions. Last year they were just stealing the plows. They caught that guy because someone put a GPS tracker on his plow.
Tom Morin does not need to defraud the insurance out of a lousy 150K worth of pickup trucks.
He has Millions of $$ in equipment & properties all around the Nashua area.
Not to mention he's a pretty stand up guy.
A lot of his employees have keys to the trucks.
Like you said, since the keys were probably easy to get ahold of, the thieves decided it was easier to steal the truck to get the plows (and whatever else was on the trucks) rather than waste time disconnecting and reconnecting the plow to their own truck.