I don't know the source you're quoting, but it's pure spin. The tax fraud and reporting violation were in direct service to the need to hide his foreign payments from Russian interests. You're also forgetting his guilty pleas for failing to register as a foreign agent (Russia again) and witness tampering (which is criminal obstruction of justice!).

This is all directly related to his work for Russia and Russian interests, in exactly the same way that Al Capone's famous tax evasion conviction was the result of his operation of a criminal organization.