Since we (as old Rummy said) do not know what we do not know, we cannot be certain about the extent of cyber attacks and what they might have influenced, and may not know these things until discoveries decades later, if ever.
I believe the popular sentiment is that when they hacked the DNC they found a handful of things that would provide bad optics for the party. But the RNC? They found so much evidence of criminality that near to the entire party flipped positions on issues related to Russia. So we have 2x successful hacks, one of which yielded some bad press for the Dems, and yielded an entirely compromised party in the Repubs who now are being actively blackmailed.
Good. But the parent was blaming Trump on disinformation propaganda, and it is important to point out that the remaining 1/3-rd of the country is not some kind of idiot army that replaced their brains with FB propaganda. They voted for this actively.
Also, in a democracy you don't get to disavow 1/3rd of the population that didn't vote with you.
Not if the election was stolen. There was a smattering of evidence after the election but the speed with which is disappeared was truly something to behold.