These unions and businesses had signed the contracts. Are contracts to oblige the workers but not the employers? Is it what "free" market is about?
There are few limits to what one can promise in a contract, but I have zero sympathy for idiots who agree to a contract where a party promises things that they cannot reasonably deliver. Any damn fool who goes along with that deserves to get stiffed as an object lesson to the other fools in society thinking about doing the same thing because someone promised them the moon.
Any employee who agrees to a contract without doing due diligence on the terms deserves whatever they get. The unions got greedy and did not look too closely or think too hard about what they were agreeing to.