There is that little law about not reporting cash or securities when travelling. I think the amount is anything over $10,000. If this were a legit transaction, the insurer has requirements about courriers and such. I don't think Don Johnson falls into those regulations. If that stuff were stolen, the insurer would deny the claim.
If it were gang, mafia money it would have been escourted by some muscle and firepower.
This money was being smuggled by Hollywood types so they would not have to pay taxes. Don was just the bagman.
BTW, the reason for driving the car is that flying chartered jets leaves a transaction trail via the air traffic system. Those movements are on record forever. A sunday drive thru the alps is not.
Hope the Feds are tapping all of his phones. When Jollywood wakes up, there will be quite a few peeps with their panties twisted over losing their money.