One of the more fascinating anime cancellations was that of Medabots, it was one of the few franchises that gave Pokemon a run for it's money mostly in Japan especially in the late 90s early 2000s but there are at least five major moments that cost Medabots dearly and all of it can be traced to the abysmal season 3, Medabots Spirits.

1. Beloved characters were removed.
Season 3 removed Henry, Koji, Sumilidon, Karin, Neutranurse, Rokusho, and Mr. Referee.
While Henry's arc was complete he's still one of the strongest rivals for Ikki.
Koji while I wasn't keen on still served a role as another rival.
Sumilidon is my favourite Medabot.
Karin was a fascinating character who really caught people by surprise with how off the wall she could be, she's like Princess Peach as a child.
Neutranurse was a mechanized Nurse Joy.
Rokusho is always the mascot next to Metabee, in fact a high number of games with two versions often had Rokusho as the cover mascot.
Mr Referee is an absolute legend.
What we got was no.2
2. What replaced them was terrible.
Other than Dr Aki's grand daughter, every new character was awful, I remember nothing of the new characters.
3. The upgrades to Metabee made him look like a toy.
My memory is plagued by Metabee being turned into an RC car, to elaborate, Metabee had an upgrade where his limbs had wheels, so he'd go on all fours, he looked like a large RC car making him look like an actual toy, a strange criticism to make about a toy anime but the whole point is to make them seem real, this is the same series that has a subplot about Medabots being murder bots don't forget.
4. 2nd Season felt like a true ending.
There was a sense of finale with season 2s ending, the only thing that really needed to happen was an epilogue to complete every character's story arc much like how Precure does it for their final episodes.
5. The franchise was already dying.
The bigger picture is that Medabots was a zombie franchise, it was existing in stagnation with endless games, two of which released barely months apart, (sound familiar Pokemon Scarlet and Violet?) It didn't help that toy anime were kinda losing their way, it wasn't just Medabots either, you can make convincing arguments for Beyblade, Yu-Gi-Oh, Bakugan and Digimon as well.
To this day, Medabots was an underrated franchise that failed to stay relevant despite the best efforts of it's makers.
It's a warning to all anime who take their audience for granted.