Putin- Trump exchanged positive words about each other.
Trump has financial ties to Russia.
Paul Manafort has ties to pro-Russian politicians.
Trump flirting w ideas of not supporting eastern European NATO allies.
RNC eliminated references to arming Ukraine in its fight with Russia from the platform.
DNC leaks day before the convention and has Russian fingerprints all over it.
This doesn't prove anything concretely but optics are bad.
Your reasoning has one fault: it is too primitive and straightforward.
Suppose Putin planned to make his candidate US President. Would he be so primitive and straightforward as to praise his agent? Not at all! He is cunning enough to praise some other candidate to divert public attention from his agent. Hence trum is a dummy used to divert attention from Putin's agent who actually is Clinton. He knows her very well, he worked with her for many years, there are close ties between them.
Any objections?
At the same time, you overestimate the mental capacity of your dictator. He is powerful, and has very smart people around him, but he is not the brightest.