But GP wrote about being replaceable being good for your career - which doesn't make sense - and the opposite what you did, which does make sense.

About your career path - kudos to you, but my experience has been that willing to do the work nobody wanted/could resulted in receiving more of said work, but when it came to taking credit, people always came out of the woordwork, on the other hand I have had many negative interactions, like the guy who knew I was an expert at some sort of thing asked me to take on a bit of extra for his sake, and when I told him I already was doing the workload of 2 people. He then told me if that meant that I couldn't do it today, it would be fine as long as I did it tomorrow.