Judging from the anger of the second driver, the scam is to steal the load and resell it on the black market; the driver must not have known what he was picking up? Or maybe they just take an up-front payment and disappear.
Why Tristan bothered taking the loads to the storage facilities instead of just throwing them out the back is a mystery. Or why the storage facilities accepted them without some kind of payment.
The key to the whole scam is that the shipments are cross-continental and that there's no observability into where the shipment is during that time. The scammer immediately drops off the load at a storage facility, which begins to bill for storage time, several days later, when the load is supposed to arrive on the other side of the country, the owner comes looking for it and the storage facility presents the owner with an invoice for storage time that wasn't originally needed. The owner pays the storage facility, which sold storage space that would have gone unused, and the storage facility pays the driver a finder's fee kickback.
It's a variant on the squeegee window washers' scam. Pull up at the stoplight and the scammer starts washing your window, then demands payment for a service you didn't agree to. Victims pay because the amount of money is too small relative to the hassle of being held up, not because they (didn't) freely purchased a service that they got real value out of.
