The reason ETH goes down exponentially when BTC goes down is because companies who issued ERC20 tokens and received ETH in their ICO's have to pay for shit. I don't think you can single out EOS because when the funding your company raised is cut in half over a couple weeks due to market conditions, and especially if the SEC is breathing down your neck, you at least have to try to not lose all the fucking money before you can get a product out.
As much as we want to think it can't happen, ETH could go to zero tomorrow if the right people wanted it to or any other number of reasons. Nobody knows what it's 'worth' because it doesn't have any of the usual things used to back up it's valuation. Analysts are still trying to make up bullshit metrics to value this shit.
The fact people were/are throwing money at these projects is a function of demand for speculative instruments/returns in a low interest rate/high instant gratification environment. At least Dan is likely to put out an actual product that works.