MM's make their spread whether the price is increasing or decreasing. They win on both the sale and the buy. MM's have no idea what the price is doing - and they don't care. The ONLY thing MM's care about is that people are buying and selling. In the absence of that, they must keep the market liquid by buying and selling between themselves.
The OTC exchange is fully automated. Trades happen by the millions, every single day, by all the MM's. You can SEE how many right here on ihub if you just look for it. The point is no human eyes see these trades. No one sends 'signals' or 'manipulates' the price. They are not traders, they are like cashiers. They takes your money and gives you your merchandise - shares. They keep a tip for themselves because they can trade at one more decimal than we do.
The most important point, again, is that they don't care what share price does - they only care about buying and selling by shareholder. That's called liquidity, and that ensures their profit.