I don't think Bill Still was bribed, I believe he honestly thought Quark was a good investment due to it having more secure hashing than Bitcoin (this is from what I remember him posting on his blog).

I think Quark was done in by a massive FUD campaign followed by the launch of Dogecoin which opened up the floodgates for the sea of shitcoins that we have now. Now everyone realizes just how fickle the crypto landscape is... it is very difficult for a coin to make it because if it starts to show signs of success, it is quickly met with non stop FUD, clones and competing shitcoins. Not to mention the latecomers screaming that the coin is not fair because they missed the boat. I remember there was even a coin called "FairQuark" for a while.