Well, first of all those vehicle remains if recovered would last maybe 30 minutes above water before they turn into brown dust, unless a long-term (and expensive) conservation program is undertaken which involves keeping them submerged in water of which the salt levels are slowly reduced over the course of 3-4 years.
And even if that would be done, all that would be left are some rusted frames and parts of relatively common trucks nobody except weirdo's like us would be interested in, all kept in an expensive building with a paid staff etc... Whilst now they attract lots of people that may not have an interest in military items as such, but just want to dive to wrecks. They would be mad to try to recover that cargo!