Because they don't know what are they talking.They don't know how bitcoin works.. In my opinion, they say btc is dead to discourage other people not to use it.  They don't  know how to use or what is the importance of having on it.

Those people trying to get panic other bitcoin holders   just to sell and buy in a cheaper rate. Some people lose their money so that they create nonsense news like this. Instead of believing that btc is dead better to research about bitcoin and believe that those impossible things can make  possible in the future.