While I'm sure that there's a lot of truth in this (and love the petition, as it focuses on shareholders, not the employees), the margins Coinbase was having for trading cryptocurrencies was unsustainable, and the company was overvalued.
Now the controversial part: Coinbase had a valuation of 100k BTC in 2012, and had the same valuation (100k BTC) at the IPO time. Unlike the internet where most of the valuecis captured over IP protocol, with Bitcoin I expect the base layer to capture most of the value, and not the companies on top of it.