Really - you are comparing apples to oranges.
Obama was fulfilling his role as president and negotiating.  Sorry - not treason.  It is called governing and statesmanship.
Trump (allegedly) - his team made promises to swing an internal US election - which is both criminal and treason.  Whether and how much Trump knew, authorized, or ordered - to be determined.  If collusion all the way up to Trump is documented and proven, he will be impeached.