I don't know what kind of campaigning itinerary there was - how much in advance everyone had to know the rally's location, but it looked like a rural location, where only few people would know intimately - unless it was a fairground type location that routinely holds gatherings, but in absence of that, how could a hit on Trump take place with security - the security itself would have the best intelligence, and authority over the area where the attempt took place.
So it was a failure. What's left? Intimidation.
So in all but declaration, we are shown that this was a set up. And if a failure happened, the apparatus for it to happen again is still in place - weighing on Trumps mind, as well as those around him. It's like a terrorist aftermath which strikes fear that looms over the present course of this country. Well, that's nothing new, but it has reached the level of assassinations of leaders.
So we know as well, without declaration, who they are, and we too strike fear in return to them, by not being afraid.