Why is Riot still owned by Tencent?

I thought the reason for them buying out Riot, is so Riot would have the funds to continue to develop League of Legends (And Riot Games in general) and make it the Masterpiece Polished game it is today (It's the most played game in the world).

But I see no reason on why Riot would continue the partnership, (Considering they made over $1,000,000,000 in 2014) Is the partnership necessary to have a server in China? Are they not able to cut loose the agreement?

I can't just help but feel Tecent holds back Riot, by forcing them to monetize the game more (Releasing Skins A LOT more instead of putting resources into other things, such as new modes, maps, new games, etc.) Whether this is true or not , I don't know, but Tencent does take a hefty profit from Riot (90%).

Feel like Riot could further develop their company A LOT more if they lose the ties they have with Tencent (If possible I'm not sure).

But Idk, maybe I'm wrong, maybe Tencent provides a lot for Riot and helps them develop the game and company, but considering the company is from China, seems like they would more then likely be pressuring Riot into making more money, then actually developing their company further.

Thats my personal opinion, I'm not an expert in the business world or how these agreements work. (Whether or not they can actually cut loose ties with Tencent) So please, if I'm completely wrong about this, I'd love to hear why.

Would Love to hear a Rioters Opinion on the Topic. If at all possible