The real problem is failure to disclose on a government form that expressly requests disclosure of the fact of the meetings/communications.  Boiling it down further, at the time, Obama was President.  The US government was fully intact.  What do we call it or consider it as when a non-governmental official, without security clearance, NOT under the purview of the National Security apparatus (and, apparently actively seeking to circumvent it and hide activities), and unauthorized by formal governmental processes  seeks to engage with an adverse foreign government to undermine or contradict the policies and actions of the then sitting US President?  What would we call it if someone did it now?  Treason?  Sleeping with the enemy?  Espionage?  etc..?   Any possiblity that things were improper DEMANDS investigation.  National Security, after all, is at stake.