Excellent article.
Yes, though many would attribute to malice what is incompetence, the latter is even more frightening. It's as if security (in general) is a victim of the Dunning/Kruger effect writ large, and that leaves no room for peace of mind.
Personally, there is likely far more depth to the incident than its most glaring surficial failures, not only failure on the ground to secure the site and ensure communications, but the apparent inability to prevent the event, but somewhere in the past of the perpetrator there is that event or impetus that propelled him on the path to the radicalized felon that fired until silenced. Without the information, the question lingers of whether the deceased suspect was the only shooter: without the ballistic remains and analysis accounting for each shot, we cannot be assured that only one rifle was used by only one shooter. Early on, someone did an analysis of report/shot sounds and determined that some of those shots originated from much farther away than Crooks' position, which might mean there were two, and Crooks may have merely been the patsy who died to cover the shooter's escape, even if Crooks did kill and wound others besides Trump.
Like you said, nature abhors a vacuum, and theories will rush in to fill the void a lack of information leaves. It is a pattern that seems to repeat in some of the most curious cases, including the Las Vegas shooter and others.
Thanks for another well-delivered ration of food for thought.