If I remember correctly from Shai-Hulud 2, the attacker extricated creds by posting them in public github repos with minor easily reversible encryption. I believe it was double b64 last time.

I'm assuming the logic there is that every security researcher and company is going to pull and scan those creds for their stuff and their clients' stuff. So the attacker is just 1 of N people downloading it. As opposed to trying to send it to their own machine directly.