It's worse than that, if unions and government were inherently aligned it'd be easier to cut the head off the snake.

Got an anecdote locally where the teachers union is running an op against the superintendent who is trying to do some reasonable things from a tax-payers perspective. Things he's doing wouldn't get tax payers a refund or anything unthinkable, but their money might actually go a little further in terms of service quality... doing so would comes at the expense of union dues.

They're like any other special interest that uses central governance as a battlefield.