Did you grow the site into 8 figures or brought on board? What was the site doing? I would imagine management would be terrified of reliance on one, bus-getting-hit-by developer.
I've seen companies with 7-8 figures and reliant on just 3-4 devs with unique and non overlapping abilities. It's more common than you think!
Now we have more developers, for which I am very thankful. Unfortunately, way too much knowledge is locked up in me, and I never have time to commit that knowledge to bits, paper, or oral history.
Believe me, buses and beer trucks have been discussed as possible ends to my consulting gig. It is my fondest hope that this business has key-man insurance on me. I'd be pleased to know that they have such insurance, but less interested in knowing how much the policy is for!