For much of the same reason he prefers your girl Tulsi over any of the other candidates. A young green politician who is openly saying and accusing the other candidates of over exaggerating Russian influence and interference. Romney was hard on Putin and Obama felt like he wasn't as much of a threat as Romney was declaring. A mistake Obama has admitted to.
Way to be overly disingenuous, especially considering all of the candidates with the exception of the "White Pants Suit" would agree Vlad is an evil villain with an agenda.