What's the full story of their feud?
Or at least a cliffnotes version? A classic money/fame/power creating a rift story or was it something different?
Axl has a lot of issues, clearly. The dude believes he was molested by his father when he was two because of recovered memories while going through past life therapy. So, yeah... Take someone who has issues and throw in all the money and fame the world has to offer, and it's not surprising the results aren't great.
Once GnR got huge, he convinced the rest of the band to sign their rights to the band away under threat of ending the group. They all did, and he went full on crazy rock star taking control of everything. How they didn't see that coming, who knows. Probably 'cause they were doing mountains of drugs.
The final straw that got Slash out of the band (according to his book) was Axl wanted a buddy to record some extra guitar stuff for You Could Be Mine from Terminator 2. Slash didn't want that, but then when he heard the final version of the song, it had guitar parts he didn't record. So, he got pissed and left.