Sure, people are gullable, and that's my main point. I don't have special insight as to who was actually coordinating the social media disinformation efforts, just that it was massive and almost entirely in support of Trump.
I actually spent a fair amount of time on Facebook at the time, and watched people falling for the crap that was going on. So, essentially users would get several friend requests from odd people supposedly living in your community, and most people would accept. No big deal right.. Well, once they've been accepted, everything these new "friends" have posted, liked, and commented on became part of your "news feed". This isn't the point where anything seems odd.
These new "friends" were also members of larger groups who by all appearances, support a candidate or a cause. These new "friends" have access your interests and the list of groups you were already a member of, and instantly profile you. With this information they could decide which of their tailored groups you would likely accept an invitation to... Whether it be "America for Bernie" or "God Bless America" etc.. name a cause, they had a group for it. You would receive invitations to these groups based upon which aligned with your interests. No big deal, your news feed has been infiltrated, and you unwittingly joined a group that looks as if it supports just what it describes. All the while your real life acquaintences in your community are being targeted in the same way.
At this point, the disinformation campaigns are already underway in these dubious groups, but just subtle suggestions between members of the groups, most who are not real people at all, often accompanied by a funny suggestive picture. All the while, you see these interactions on your "news feed".
As the number of real people who join these groups grow and election day draws near, the disinformation and propaganda level of these groups and interactions steadily grow. At this point your Facebook feed has transformed to a degree that it's a steady stream of politically motivated influence and disinformation.
A week out from election day, these groups and "new friends" have gone full-on propaganda/meme trolls. "America for Bernie" is now incessantly posting about Hillary killing people, and suggesting she'll be in jail by election day. "God Bless America" is doing the same and mixing in some Pizzagate... The scale of this being the whole country with emphasized targeting of communities that polling data suggests are integral.
Was this being done by Russia? I cant tell you, but the planning, coordination, and execution were surgical.