BitMEX isn't a spot exchange. It offers derivatives and futures products. It does has its share of issues (namely system overload) but it is probably the only legitimate platform (i.e. no fake volume) on Coinmarketcap that doesn't get volume counted because it is not spot volume.
The elephant in the room is that the liquidity and trading on BitMEX is legit and many times higher than spot, yet BitMEX is unregulated. Big players can and has used BitMEX to manipulate spot prices (arbitrage/market maker bots will move the price on regulated spot exchanges accordingly). It used to be that most of the manipulation happens on Okcoin futures products. Since the China fiasco in 2016-2017 they lost almost of all of their traders to BitMEX.
The elephant in the room is that the liquidity and trading on BitMEX is legit and many times higher than spot, yet BitMEX is unregulated. Big players can and has used BitMEX to manipulate spot prices (arbitrage/market maker bots will move the price on regulated spot exchanges accordingly). It used to be that most of the manipulation happens on Okcoin futures products. Since the China fiasco in 2016-2017 they lost almost of all of their traders to BitMEX.