Did Putin have him killed? Probably, but it could have been another Commie goon. Vince Foster may have been murdered on Clinton’s orders, or maybe someone else iced him. Same with Bill Colby, Ron Brown, Sasan Chaffee, etc. No solid proof, only speculation.
But I will give the Clintons the benefit of the doubt on Navalny--I don't see how his death would advance their interests.