https://www.boredpanda.com/employee-quits-work-messes-with-vacation-boss-losing-money
Totally insane, not just because it happened, but because this kind of stuff happens so often in so many places. It's a long read, but worth it.
Lots of lessons learned here. One of the biggest is that if your company is losing money hand over fist, it's not time to quibble about a few bucks to retain a key employee.
That guy received regular 3% pay rises?? He was so lucky! Never have I ever received regular rises and I received 0% rise for the recent 8 years.
I'm not sure about the 2 week (or rather, notice period) resignation part, maybe he's in the wrong there for no notice period I don't know. He could have still gone on leave regardless and gave notice at the same time. But he seems very mature about it. The manager and company is putting all of their problem onto this one guy.
Just let him spend his Christmas with his family and don't run the business that way in 2022 and problem solved.
In the USA, at-will work arrangements mean that the 2-week notification is customary, but not required. It burns a bridge, but it can be done. I've done an "effective immediately" resignation when I left teaching for going back to IT.