Reasons I have seen webcomic authors publicly cite for cancelling their comic mid-storyline:
Too busy
Lost interest
Increasing age gap between characters and author made it difficult to relate
Did the math and figured out that completing the planned arc with their current update schedule would take 150 years
Ostensible author actually a fictional persona that’s now being retired, and they didn’t want the comic linked to their real identity
Realised that the way they’d written the central relationship wasn’t emotionally genuine (note: this was a hobbit porn comic)
The comic’s readership contained too many lesbians
Converted to a religion that regards all representational art as a form of idolatry
Broke up with the person the protagonist was based on
Outed as not actually Japanese
Imprisoned for manslaughter
Aliens
