Not necessarily. The employees may have been stuck between a rock and a hard place. If amazon sent your whole team messages saying they'll hire you or crush you, taking the job at amazon might be more like trying to keep your job. Especially as others start to take the offer. The only thing saying the bonuses were nice bonus was the "hey come join us" email, and we all know what those are worth.

One of the people involved said he didn't take the offer because he didn't think he'd get the same benefits. Since the contract stuff was about royalties, it might be that joining take-two meant trading royalties for salary/bonus, and as interest grew in KSP2, that might be a shitty deal.

Because it was cheaper than dealing with their current employer. All about controlling costs. The bonus was carefully calculated to balance the development costs versus contract costs.

Those employees can expect precisely nothing once the game is complete, unless coincidentally their new employer has another project they can be immediately put to work on.

That would have been the same result after the game was finished either way, given that Star was only a contractor.

At least at Take Two the employees have the possibility of working on other games.