Putin is going to take down Trump by dumping the evidence any day now, probably within days of the sanctions bills passing, and Mueller and the legal system will be his instrument. That seems almost certain at this point.
Whatever classified evidence exists will stay classified, so if Trump is going to go down in complete Hindenburg fashion, Putin will be the one to do it, and there'd be very little downside for him. He just wants to see America undermined and he knows no one will declare war on him, regardless of how much he meddles so if he's already under sanctions, what's the difference?
Maybe he takes Ukraine while he's at it. He seems willing to take things far past the point of mere saber rattling.