Here's a common situation from programming. A programmer, Steve, works long hours but writes sloppy code. Steve is often seen by management fixing critical issues in production, and 'saving the day'.
Eventually Steve, leaves to work at a bigger company and is replaced by a new programmer, Dave, who is more methodical. Dave eventually cleans up the code and gets it to run smoothly. The problems in production go away, and Dave can work at a leisurely pace.
Management will typically think to themselves: Dave is pretty good but that guy Steve was a real rockstar!
Humans are biased to like stories. The story of Steve slaying software dragons[1] is just way more compelling than the boring tale of Dave watching a machine smoothly do its work.
When that company hired you to work for them, a subtext of that arrangement is that you were both going to go on a quest together. I believe this to be a deeply embedded bias in human thinking, and that it explains part of why they were miffed.