I agree that life goes on, but it's not rare at all. It happens all the time. People leave and things are f-d up for a while.

The thing is, it's not a permanent condition. People adapt, new hires are eventually found to fill the gap, or others who were thought of as not up to the task take the opportunity left by someone's absence to step up in their career.

One person leaving won't sink a company that is large enough. That doesn't mean it won't hurt, however. And how the company handles things after the departure is very critical.

Perhaps more important (and dangerous) is the morale hit that the others will feel as their peers start leaving. There very much can be a "rats-leaving-the-sinking-ship" effect that can be precipitated by a key person leaving.

Oh, yes. One person does not sink a ship, but I've seen cases where whole teams leaving destroyed companies.

And while I was under no illusion of my importance and did not expect any breakdown of the team or anything like that, I did think I would get at least ONE question after I left from my previous teammates about some obscure thing that I thought only I knew.

Nada. No one asked me anything - they had no issues for which they had to reach out to me. Team did a re-org and things just kept moving. It was a humbling realization to say the least.

More likely no one cared.

It also depends how regimented the team is, places like Amazon have large numbers of coders on the same project, watching over each other. But they also compensate their employees well.