Suddenly Coinbase is bigger than Finex and Bitstamp

I remember some weeks ago they had really low volume
No. Since they started charging fees they have lower volume than Bitstamp. Coinbase ask side (and bid if we take out that wall) is still very thin. Don't know why would anyone wire 1mil$ to the exchange with such low liquidity.
If I was sending $1m anywhere, I'd want it to be somewhere with at least a degree of regulation and in my home country, not somewhere like Stamp of Finex that might run into problems of some sort.