Lots of reasons and excuses, but it comes down to the fact that Lenin drew bad national lines on purpose (gave ethnic territories to the wrong country in order to have ready-made ethnic instability on-demand).
Diabolically clever, if true. (I didn't know that).
And, Churchill marked up the MidEast and produced similar results because he was in a hurry. I remember reading that after WW I, he carved up the Ottoman empire's territory on a map in an afternoon.