The incentive is plain and simple. He stole them just prior to almond pollination in CA. That is an immediate $180 per hive in his pocket. His total take of stolen hives is thought to be about 1000 so $180,000 for a few nights work.
Re how bees are treated in almonds, one of the guys who had 480 colonies stolen is a top notch beekeeper who cares for his bees. They were his prized possessions as well as his only source of income. He had them scheduled for almond pollination followed by return to North Dakota to make a crop of honey which would have produced another $200 or a bit more per colony. The low life slime that stole them literally stole his livelihood.
Tveretinov had a LOT more than 100 colonies. It looks like he was running about 1000 stolen colonies and had about the same of colonies he built.