That is trading volume, not liquidity. And we should be wary of the trading volume on bitcoin exchanges, a lot of it is manipulated. (In particular, I would never trust any numbers coming from Bitfinex)
Coinbase is not a sketchy exchange by any means, and while I'm cautious about Bitfinex their volume is quite believable given they are the default choice for non US persons.
That's also why I quoted USD, if you include crypto-crypto volume and some of the zero fee exchanges it definitely becomes nonsense.
The linked article even cites one hodlr that purchased a professional hockey team with his crypto profits.