Dealers get wheels stolen all the time, rarely inside job.
Back in NJ I had heard of a crew who would basically take orders then one night just go hit a bunch of dealers. They would start by going to a uhaul location and stealing the keys from the night drop box take a van/truck whatever. They would then go to a construction site steal a bunch of materials to sell as well as cinder blocks. Then they would head to the dealer and take the wheels leaving the car on the stolen cinder blocks.
This was late 90s but I'm guessing the same still goes on all over.