WannaCry hero arrested, tracked via bitcoin (BTC) transactions....

So as some of yall heard today, apparently the WannaCry hero was arrested today and somehow linked to the actual WannaCry virus? The story was published with some very vague info so far, but apparently the FBI was able to get a warrant to arrest him yesterday based on his transaction history leading him to the withdrawal of the btc stored on the wallet that people locked down by the virus paid ransom to. The btc was removed from the wallet shortly after the fork occured the other day....could it be the same guy who designed the virus that locked down so many computers worldwide, then went public about knowing how to stop it... was the same guy???? or is this a cover up to make people feel better about the person going unfound up tell now.

My question is this, if digital currency is suppose to be so anonymous, how are they claiming they followed his transactions to link him to the wallet?