It's obvious what they gain? What does the CCP care about more than anything? They care about their image and the stability of their hold on the people.
If China looks like they "fucked it up" then the people become more restless and start questioning the party. Also, they care deeply about their worldwide reputation and that the world sees that their "system" (top down authoritarianism) is seen as more effective than western progressive liberal democracies.
It makes them look a hell of a lot better if they can say to their people, "Look guys, look at how well we handled this crisis compared to the Western countries, this is why having an authoritatian one-party state with absolute control is better for you guys!"
Looking like the idiot country who totally fucked this up doesn't help the CCP at all, which is why they tried to silence the guy who was originally trying to blow the whistle on this whole thing.