NBA players can't "be bought easily". The reason why this was caught after two games is that betting anomalies are immediately exposed. Dumb decision by Porter. He is expendable, and his career in the NBA is likely over. Every NBA player knows, or should know, that when the betting handle (the total amount wagered) on a player prop spikes, red flags will fly and investigation will ensue.
A group of guys in Ohio got caught for an unusual betting pattern in an Alabama/LSU baseball game. Fixing games does not work for the player/coach involved or the bettors involved.
Also, "many refs" aren't on the take. The Hornets just suck. The reffs have jobs which they love, and are easily replaceable. If a ref is fixing games, they are done, and may go to jail like Donaughy.
The sports books are in this to make money on fair games; the odds are slanted in their favor. If the games are fixed, they lose. So, they have vested interest in ferreting out any odd betting patterns (e.g., games that consistently go over with a certain ref; or enhanced action on Jontay Porter props; or a group of big bets against Alabama baseball in Ohio). These fixing scams never work out well for those involved, and those involved are the ones that are too stupid to understand the measures in place to catch fixing.