I think it's going to be difficult to drill down to the bedrock of this incident, because we're already seeing highly biased, deliberately slanted, reporting even in the mainstream media. The crafted narrative depends upon your agenda rather than the facts.
NPR had to walk back "the worst mass shooting in US history!" when readers and listeners kept calling them on it, many pointing out Wounded Knee and other brutal massacres. NPR eventually called the guy who literally wrote the book on the history of mass shootings in the US and he said their phrasing was "sensationalistically serviceable, but disingenuous." He noted that mass killings before 1900 tended to be mob-oriented hate based, while after 1900 they tended to be individual-oriented hate based. Said at the very least they should include a time frame, such as "in modern history" or some other valid qualifier.
ABC News, on the other hand, spent 3 days meticulously deleting all Wounded Knee and similar references that didn't promote the "worst in US history" narrative from the comments section of their story on the matter.
Some see this as both an act of terrorism and of hate, partly because pretty much anything these days is classified as generic terrorism, and because gays were involved. Some see it as pure Islamic terrorism. Period. Some see it as 100% pure homophobia. Period.
The FBI (fighting terrorism is our business, but boy do we suck at it) characterizes the shooter, his wife and kid visiting Disney World as "scouting locations" and characterizes 2-3 visits per month over the past 2 years to the same gay nightclub as the same "scouting" of locations.
I think his nonsensical pledge to ISIS, along with other groups who are enemies of ISIS, was a lame attempt to use terrorism as just a justification. He was a not-particularly religious Muslim American who was filled with self loathing over being gay, who suffered narcissistic injuries, who lashed out not because he was filled with religious fervor, but because he was a terrible person, insane, and looking to destroy that which tormented him. In my opinion, Islamic extremist terror is a red herring cloak in all this.