Sundering stuff established in the Q&A

[Skyborne]

I feel it's more that they built Elidibus up to be too good an opponent previously, and they couldn't find a way for the protagonists to convincingly beat him so his ability had to be undermined instead.

(And then took a further jarring shift with Tales From recasting him as an "adoring younger brother" type to the group, which is... what.)

Additionally, his presumed role in Pandæmonium means that he doesn't get to appear in the credits "passing the torch" scene with the others, because they can't officially show him as an ancient and identifiably Elidibus yet.

Elidibus in 2.x: Scheming manipulator who always seems to be a step or two ahead of the heroes, mysterious, seems to have more going for him. May or may not 'help' us. Told Nabriales to not harm Minfilia, and attempted to put a leash on Lahabrea.
Elidibus in 3.x+: Essentially takes over Lahabrea's role now that he's gone, sets the stage for the 8th calamity with multiple backup plans. Attempts to take us out directly afterward, with no room for negotiation.
Elidibus in 5.x+: reeeeeeeeEEEEEEEeeEEEEEEeee I am an amnesiac hero running on fumes, I will now proceed to drop everything and just throw myself at you, ungabunga. I am also not actually Elidibus, but a copy of him reconstituted from Zodiark goo. Please be sad and clap. Though, to be fair, he actually had the smartest plan of just dropping us into the Rift to suffocate and die. Not his fault Emet-Selch decided to help us.