The correlation between supply and demand determines the fate of cryptocurrencies. In case of dead coins, it means there is zero demand for them, as no one is interested anymore. Then you can blame the developers for launching and offering something so useless that nobody is interested on it.

In fact, many of the dead coins were solely created with the purpose of launching temporary hype, so developers sell their personal holdings for quick profit, turning their native tokens into Bitcoin, stsblecoin or any other consolidated altcoins, while majority of investors (the late ones) see their personal investments melting to zero value by holding such useless tokens.

On the other hand, you can also blame the investors for being greedy to invest in a product fully dependant on speculation to survive.

After all, you can put the responsability over anyone or consider it just a natural process of a decentralized market. The most important here is to avoid investing in such tokens at all costs.