IMO this move to replenish traders was a mature business decision that many tech companies would have failed at let alone crypto companies. There is massive money in the long game for Coinbase/GDAX, and providing real and imaginary assurance could cement them to become the Visa of the next decades.
From GDAX's point of view the tradeoff boiled down to whether to invest in PR / brand today or risk a moral hazard problem in the future (users expecting bailouts so they take more risk).
I would never do such (I consider it unethical, but more to the point I have neither the capital nor risk tolerance to pull it off), but I wonder if someone might. Or perhaps already has.
1) Flash crash 2) Horrible customer support 3) Delayed Ethereum widthdrawals when the network isn't under stress
They have a lot of problems. They may be happy to spend the money to clean up one of them.
See 2010 flash crash. "Procter & Gamble in particular dropped nearly 37% before rebounding, within minutes, back to near its original levels. The drop in P&G was broadcast live on CNBC at the time, with commentator Jim Cramer commenting."