Jim Lee was brimming with ambition in those days. He made moves. Editorial sided with him, and pushed Claremont into a corner. Except, even when Claremont was gone, it wasn't enough for him. Just half a year later Jim jumps ship to found WildStorm/Image. Ambitious.
Harras was dumb, threw the baby out with the bathwater, got played by Jim, and presided over the implosion of the once unstoppable comics line(Were it not for the success of TAS, floated largely on the strength of Claremont's characterizations and stories, the line would have imploded even faster. I mean, it didn't even take a whole decade before they had Claremont come back....).
Claremont could understand Jim's youthful ambition, and wisely understood Harras and Marvel as the true villian(can you imagine the sense of betrayal after 16 years of spinning straw into gold for those people??). Besides, at the end of the day, Claremont is always pragmatic. If Jim reached out to work with him at Image two years later, of course he's going to take the job(all the better if it helps erode Marvel's market share at the time). Only a few years later he's writing for them again. Even when the Fox films butchered his characters and stories, he towed the line. He's pragmatic more so than egotistical, despite having been used and abused by these companies. Given how a lot of writers operate in this industry, that kind of professionalism is rare(especially when no other writers have accomplished what he has).
I hope Feige rolls out the red carpet for Lord Claremont if society doesn't completely implode before he gets to the MCU X-Men.