I understand this is a plea deal and we are meant to believe Flynn is being let off easy in exchange for vital evidence that blows the lid off Trump's collusion with the Russians, but...
given Flynn's other seemingly more serious legal challenges around the unregistered lobbying, busting him for something we already knew about doe not seem like an investigative breakthrough.
MORE: OK, this isn't great, but...
Stocks fall sharply on report that Michael Flynn was directed by Trump to talk to Russians
- ABC News reported that Flynn would testify that he was directed to make contact with the Russians.
Asking your National Security Advisor to speak to the Russian Ambassador (or others) is hardly illegal. As to what Trump told him to discuss or not discuss, time and Flynn will tell.
That said, I doubt Trump told him to lie to Pence or the FBI. However, it does sort of time in to an obstruction charge, especially if Mueller theorist are comfortable that Trump can "obstruct" a going-nowhere investigation of a non-crime.