You should have refused to do it or to train anyone to do it. That's their problem if they don't know how to use their own systems.

at least no one else will get laid off?

I assume you will ensure that you get all the benefits coming to you - So that’s one very minor upside… And you can look forward to your former employer floundering in the HR department for some time… Shit happens, get your resume out. Right now your main priority is in finding another job… Once you give or get notice, how hard you work at the old job matters a lot less. When I got my layoff notice and had already decided to retire I asked if I had to come in. HR checked - I didn’t. So with my final check in hand, I went home never to come back again. It no longer mattered.

You should lay off all of the management and become dictator of the company. Being the only one who can lay off people is a superpower!

I once gave my notice and was planning to stay on the full 2 weeks to help out, then my manager was an asshole to me about it... so I spent used my time to learn to do cake decorating and backed a cake with a big "**** You" on the top. I mean I learned ALOT of decorating skills while still there for this. then presented at my farewell lunch I said I was holding. my ex boss was pissed. I left a couple days early before they had a replacement. leaving a job is an opportunity to do things you always wanted to do.