SSE vs. Hang Seng

Both SSE and Hang Seng are stock indices based in China. While hang Seng is down 35% in the last 5 years, SSE is up 15% during the same time.

How is this possible? I understand that there’s no free press in China and the govt can do anything there. However, if CCP is indeed propping up SSE, why can’t they do that to Hang Seng as well?

I apologize if this is a silly question. I’m asking genuinely. No trolls please.