So basically there are two plausible explanations:

1. Someone with early access to Mythos leaked it to the bad guys.

2. Cybercriminals are getting enough mileage out of alternatives to Mythos to create exploits far more quickly, even though they don't have access to Mythos.

My own guess is that it's a combination of #2 plus vibe-coding degrading software quality at multiple layers, open the door to sophisticated exploits, but I have no insider access to Mythos so am just guessing. Maybe someone with Mythos access might say why they think this vulnerability spike happened when it did.