Bitmain was the main of the very few supporters of BCH before and after the fork.
I read or heard about somewhere [rumors] that they are trying to centralize BCH by controlling (They sort of already do), so by accepting only BCH, they are sort of increasing demand on it by forcing buyers to buy BCH so they can buy Ant miners. At the same time, they would evetually end up with most of the market capital allowing them to make it scarce when they want to increase it's price, and abundant when they want to lower it's price... Not sure how accurate or true those rumors are, but it makes some sense to me... A lot of the BCH haters also hate Bitmin for that...
It's why they got their negative trust rating in the first place. Unless they own viabtc (unlikely) then we are lucky enough in the knowledge that they won't be able to change it without making a fork of bcc and "bitmain cash" which would be worthless.
There were also rumors bitcoin cash will overtake bitcoin. This is achievable by a company like bitmain (especially if hashnest continues to stop paying or working - from the start of today they haven't paid anything)... They have enough power anyway to dominate that coin and set its value very high, if they want to, however, if they get too poser hungry, people will just turn away from them.
I'm a little confused about viabtc. Stupid question: Why would it make a differnce if they own it or not? Don't they need 51% pool power to be able to make forks?
In order to overtake BTC, dont they need to control both?
Finally, I don't understand why the mining pools still look the way they do. If Antpool BTC was 25% global BTC hash before fork, then after forsk they started mining BCC with a 22% global BCH hash, unless they doubled their mining operations, shouldn't their BTC global hash have droped by half, or at least a little? Care to explain?
Here is the
BTC Global Hash share that I found:

Source:
https://coinsutra.com/bitcoin-cash-bch/EDIT: After a closer look at the article in the source, I realized that was a BTC Hashrate distribution. All edits in are bold.