Counterratt here, I'd say it's actually Kiara/Calli's idol ambitions that drove the group apart (their schedule becomes stacked on top of spamming JP/non-holo collabs for networking). The NijiEN streamer stays close with each other because noone really have idol ambitions and just happy to play games with each others.
Ame, very likely went back to play with her old Twitch cliche because she can't find any Myth to play games with and none of them just happens to be streaming (e.g. I bet biboo still regularly plays with her old FF14 cliche, just that they finished their OPSec/none of them streams).
Same thing happens with HoloJP, their idol ambitions drove genmates apart and they found new groups to interact with due schedule misalignment/marketting, it just happens that those new groups are within hololive/niji/vspo that we don't see them disappear off the grid. Ame had less option to choose from as NijiEN/HoloEn got a weird collab lockdown until very recently.
Gen 2 is so far apart they collab less than Myth this year and already memed and acknowledged themself as Exodia.
Even gen 6 with how close they are is seeing laplus forming her own cliche off holoX. There is an alternate universe where all her valorant friends doesn't stream and she just fuck off to nowhere like Ame. It's an issue that persist within the entire company due idol ambitions.
Gen 5 is the only exception with how close they are and how hard they got ass blasted at the beginning.