There was a slightly different amount of information available in the time you call "so quickly."
Any "calculated move" that involves repeated pleas to one's own customers to withdraw all their assets from one's platform to protect themselves from that move... well, you can characterize that as well as I can.
I admit that "calculated" might be a stretch, considering how far off their delivery date is. Despite that, the original announcement could have been more realistic ("we might support it soon ") but it wouldn't have made nearly as many headlines.
It does seem like they're understaffed. Maybe they were hoping the fork would wither away quickly and they wouldn't need to deal with it. As one of the largest exchanges they should have better contingency planning than that.
I hope they continue to succeed because I do like Coinbase.
If you are going to be cynical, why not go full cynic and say they were waiting to see whether the public outrage would be higher than the value of Bitcoin Cash they pilfered of their customer base.
Any "calculated move" that involves repeated pleas to one's own customers to withdraw all their assets from one's platform to protect themselves from that move... well, you can characterize that as well as I can.