More details are needed before we can comment on this news. I am not sure how the feds were able to track the Bitcoin transactions. Drug kingpins normally have tens of billions of USD worth of turnover per year, and they are not stupid to use payment methods that can be traced back to them. I am sure that the Chinese individuals in question here might have used Bitcoin mixers and other anonymity providers.

There is a good chance that they were traced when they tried to convert their BTC to cash. And this is the stage where more than 90% of the drug traffickers are caught. There are only a very few instances where the authorities actually tracked the Blockchain transactions to the individual. In most cases, the BTC to fiat conversion is the riskiest part for the criminals.