What is the in-universe explanation for why succubi, who were demons, became "neutral evil fiends" in 5e?

Question

The Forgotten Realms wiki page on succubi tell us (specifically in footnote 1) that in 1e, 2e and 3.Xe¹, succubi were chaotic evil demons, but then were retconned to be lawful evil² devils in 4e and have now just been made into generic neutral evil "fiends" in 5e, presumably in an attempt to avoid contradicting any previous editions' lore.

Does 5e give any sort of in-universe lore explanation as to why they are now neither devil nor demon? The 5e Monster Manual entry doesn't really explain that besides briefly mentioning that they "can be found in service to devils, demons, night hags, rakshasas and yugoloths", again presumably to avoid contradicting any previous editions' lore, but without explaining why this is now the case.

This is the second part of a two-part question, which was split out from this other question post; see: What is the in-universe explanation for why succubi, who were demons, became devils?

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¹ _{Actually, the footnote on the Forgotten Realms wiki page only says 3e, but I know it was still true in 3.5e because of Neverwinter Nights 2, which was a video game based on 3.5e. In this game they were considered demons, which is incidentally my introduction to D&D and why I consider succubi being demons to be what they "should" be.}

² _{I say "lawful evil", because that's what a devil's alignment is, but I'm aware that 4e changed the alignment system, so it might not be so accurate to claim they were "lawful evil" in 4e, but at the very least, in the context of D&D overall, they would have been considered lawful evil all the time they were considered to be devils.}

Answer 1

They betrayed Asmodeus when it suited their needs.

The Forgotten Realms novel Ashes of the Tyrant (2015) suggests that, just as the succubi betrayed the Abyss and defected to Asmodeus to become devils in the 4e era, many once again turned traitor and abandoned their loyalty to Asmodeus when it suited their purpose:

"But given the rebellion of the succubi in Stygia," the bone devil went on, "the fact that the Abyss has grown more of the defectors since their defeat, one would assume that His Majesty would be glad to allow Lady Malcanthet to show where the true succubi stand."

Lorcan met the creature's green-ember eyes within its hollow sockets. "Or loath to let her conspire with her sister."

The bone devil's teeth twisted in something like a grin. "You give the succubi too much credit. The ones who remain must know it's in their interests to reaffirm their loyalties."

You don't give them enough credit, Lorcan thought. If the succubi were as foolish as most of the Nine Hells believed, they would never have escaped the Abyss when Asmodeus ascended—and if they were wise enough to see which way the wind blew a hundred years ago, they were wise enough to see it now.

I think you're correct in the out-of-universe reason, where in order to appease players of both 3e and 4e, the succubi have been made neutral evil in order that they can serve as either, as the DM wishes, for maximum compatibility and to keep the most people happy.