the workload had gotten so insane that getting fired wouldn't have been a relief.

I gave them such long notice because I was walking away with 11 years of knowledge that no one else in the company had. I wanted to do everything I could to avoid them hating me for leaving

I actually stayed 5 more months before leaving so that I could get my annual bonus and find an ideal landing spot. They ended up wasting all 5 months. The promised assistant/replacement was never hired. When I officially gave them a written two weeks' notice they were shocked. I asked about the promised assistant to which they answered that they had decided to postpone that candidate search.

This is a company that makes $5 million profit on $10 million annual revenue. They had money to make things right. My supervisor apologized within two weeks of my departure for not listening to me when I told them how bad the job had become.

I left them in a major lurch, but I managed to do so without burning any bridges.

Not that it matters. Management has created an echo chamber so bad that the whole company is now out of touch. Customers are dissatisfied and leaving in droves. They have been told exactly why but ignore the problems anyways. It's an industry with a lot of momentum. They've got their customers locked in for now, but I'm guessing that the company will be dead in 5-10 years.

Sometimes people are going to shoot themselves in the foot regardless of how much you warn them.