There's no legitimate reason to intentionally take losses (or refuse to take revenue) for tax reasons, though.

If you lose $1000 and get a tax benefit worth $200 on those losses, it's still a net loss of $800, so you should rather get at least some money back. Getting $500 back might mean that you lose $500 and then get $100 back in tax benefits, so that your net loss is $400 instead. That's an improvement over losing $800, so it's worth doing.

More likely, the contracts around the movie had them needing to pay rightsholders, actors/writers/directors, and producers based on certain formulas on the gross revenue, or would be contractually obligated to spend a minimum on marketing and promotion if there was going to be a release, etc.

Taxes just alleviate the degree of losses (or reduce the amount of profit), which can change behavior around risk taking, but it wouldn't make sense to abandon a finished movie solely for tax reasons.