Market markers on the OTC market literally "make the market" by executing trades. OTC means "over the counter"..not fully transparent on L2 or L3. Market makers are permitted to buy, hold, short as they like...they make money on volatility and by holding enough shares to manipulate prices to their advantage.
Same issues exist on "big boards" but to a lesser degree with greater liquidity. Hence the desirability of uplisting. Read up on NITE, CANT, VFIN etc...
Stock trading is rapidly being superseded by derivative trading which now constitutes 60-70% of the market activity in securities..And most stock and options trading is HFT, computer algorithm driven trading designed to foil humans and manipulate prices with massive bidding and bid canceling in millionths of seconds, no kidding. To make money we remaining non-bots have to be smart, lucky, and master emotion.