I think it's partially due to teams like NOVA getting better/moving towards their potential and outperforming established cores like the RA/JDG core. Also they might've been underestimating NOVA (which is fair). Who knows though I'm just giving the benefit of the doubt.
Even with yoman this team rn would crumble. Bruh even with yoman this team wasn't that good strategically. Just all players were firing at the time and now other teams are settling properly so have got better than jdg. Jdg still needs more time to settle with yhchen.