… because it isn't (quite).
Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.
The Congress shall have power to declare the Punishment of Treason, but no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted.
U.S. Const. Art. III § 3. Russia may be a hostile foreign power, but it is not — either under international law or by declaration of either Congress or the proper part of the Executive — an "Enem[y]."
The very best evidence that Putin would have wanted Drumpf to win in 2016 is that — after, at minimum, indictments implicating Putin's government (and, reading between the lines, personal involvement at some significant level) prepared/supported by people Drumpf on the same day declared he had "great confidence" in — Drumpf can't think of a reason that Putin would have wanted him to win in 2016. The parallel to the repeated victim of fraud not being able to understand why con artists would target him is rather apparent… and disturbing… especially given the glee with which con artists pass around lists of marks based upon their past successes.