Boikova always had trouble accepting her and Kozlovskii's mistakes, go back and watch her reactions after their 2019 GPF FS or this season's unclean programs and you can see her anger and frustration. She reminds me of Kaitlyn Hawayek in that she has no poker face. So the way she reacted after their FS at worlds wasn't at all a surprise to most, I think the surprise was that it was aimed at Moskvina of all people which came off as bratty and disrespectful.
If B/K can't learn to face strong competition they will always crumble under the pressure because they are young enough to continue until at least 2026 and new teams will rise, both in Russia and internationally. This is just the beginning of facing fierce competition, and while B/K are young, so are M/G and P/K and we've never seen them act the way B/K do.