The sweetheart deals are usually from the state, sometimes the county. Town budgets tend to be so small that ~$20m/yr will have the council falling over themselves to approve it.
The problem, from the cases I have looked at, seems to be that towns want to do dumb shit with this money rather than just cut residents a tax break.
The sweetheart deals I've seen has been the state approving things that mostly affect the locals. A large part of property tax goes to local governments who were given no input in the deal.
Or the towns are not rich enough to fight in a lawsuit after the town council initially says no, which is how my local datacenter was approved against the will of the people