Idol and other other small corps don't have a carry as significant as Phase does. Pippa may have less than half the subs of Rin but Pippa often gets more than 2 or 3 times the average CCV as Rin. This is because Rin's subs are mostly from shorts farming and we've already discussed at length how difficult it is to turn shorts watchers into consumers of clips and streams. The thing with carries is that their huge fanbases will watch adjacent content sometimes, especially if you often include their oshi. So if you put out some clips with the carries like Pippa and Tenma, those clips are more likely to get views, which helps your channel grow and do better in the algorithm for your clips of the other talents.
So while Phase Gen 3 may have had similar debut sub counts to V4Mirai's Gen 3 sub counts, Phase Gen 3 clips had an easier time gaining traction due to Phase's inherently large fanbases elsewhere. For example, I made an Eimi clip back in January (within 1 month of them debuting) and it has 50k+ views because the topic included Sakana and any clip that includes Sakana gets tons of views. I have ~1 million views on my channel and more than half those views are from clips with Sakana in the title and thumbnail. Sakana is actually the biggest carry, as he's the biggest view generator for Phase because viewers know they're going to see Sakana triggering the fuck out of the girls or getting yelled at by the girls. I've brought this up to other Phase Clippers and they've all noticed that Sakana automatically makes your video get tons of clicks/views.