One operation from over 50 years ago is your example? Back then the spooks were doing far worse, conducting operations against domestic civil rights groups.

That's a little different than a public DNI statement on behalf of 17 different agencies pointing to Russian attacks, corroborated by multiple other nations, in an era of wide-spread whistleblowing that would uncover a large-scale conspiracy.

Occam's Razor says all signs point to Russia.