Why not? Chinese people use Instagram, too. This post by a Chinese celebrity has more than 800k comments, most of them in Chinese: https://www.instagram.com/p/B1HRZMWHPvc/

Instagram is pretty much the reason 99% of the females even scale the GFW.

Generally they hate talking about politics, and actively avoid the "smears" outside the GFW.

That's why the recent pro-China posters are often deemed bots for being inactive or new, they don't like Twitter coz it's full of fake news and smears to them.