...However, soon before Uncanny X-Men #200 came out, Marvel, in their American Doctor Who comic, did two issues that reprinted stories Alan Moore had written in England.
Marvel, at the time, did not have any deal in place where you would be paid royalties for foreign reprints.
Moore, as you might imagine, was outraged. Marvel had not asked him for permission and they had not paid him. So when he then found out that Chris Claremont was planning on doing a major X-Men storyline involving his characters from his Marvel UK work, well, he was even angrier, and any chance he had of reconciling with Marvel over the reprint issue (they stopped reprinting his stories when he complained) was pretty much dead.
Now, legally, could Marvel still have gone forward with using the characters Moore had either created or developed? UK copyright law is different from US copyright law, and things were a bit sketchy but honestly? Probably. But as we have seen many times over the years, comic book companies tend to lean towards the side of being conservative about this stuff. So Marvel’s lawyers recommended just dropping any plots involving Moore’s characters.
When Claremont found out about the controversy (obviously, he did not know that Moore was mad when he began using Jaspers, as obviously Claremont planned on using the characters as more or less a TRIBUTE to Moore) he quickly re-wrote the stories he had planned, which was going to be basically a two-year (or so) storyline. Everything happened as planned for the next few issues (which makes sense, as obviously by the time Claremont even LEARNED about the problem, the issues were already being produced), including Rachel Summers leaving the book.
But soon Claremont’s original plans diverged from what happened in the comic. The original plan involved Nimrod merging with the Fury to form an astonishingly powerful villain. This new villain would wipe out the Morlocks and most of the Hellfire Club. In the various battles with the X-Men, he would also severely wound Nightcrawler. Ultimately, Kitty Pryde would temporarily defeat him by phasing through him, messing with his circuits but the reaction would have left her injured, as well.
Nightcrawler, Kitty, Colossus and Longshot (hot off of his mini-series) would leave the X-Men to go to England where Colossus would serve as a bodyguard of sorts to the recuperating Kurt and Kitty. This, naturally, would lead into a new book called Excalibur.
Jaspers, meanwhile, would team up with Nimrod/Fury, and slowly turn the population of the world against the X-Men. Mutants all over the world would be forced to team up together. Eventually, Forge and Roma would get involved and the Siege Perilous would be used to defeat Jaspers and Nimrod/Fury, but the X-Men would be warped via Jaspers powers so that Claremont could make various changes with the team.
Now, obviously, once you have to remove the Fury and Jaspers, things has to change dramatically. Instead of Nimrod/Fury killing the Morlocks, it became Mister Sinister and the Marauders.