They're not buying the commercial tractor-trailers they're just operating them with CDLs California issued to them without even having enough basic English knowledge to read road signs, with predictable results.

Of course this is partially a problem of the government creating the problem of disqualifying Californians who could perform the job. Like 40% of California smokes weed but recreational use disqualifies you from a DOT physical for interstate CDL driving eligibility, and probably medical too though for not much longer since it's now schedule III and the DOT just hasn't caught up with the rescheduling yet.