To really study this in terms of conspiracy vs incompetence, we have to consider that there were two moving parts at play.
Part 1 is the Law Enforcement Response/Security Protocols
Part 2 is the Shooter/Motive/Behind the Scenes
Most of the theories I've seen floating around treat these two parts as one and the same. However, each one could theoretically be independent of each other. That is, incompetence on the behalf of Part 1 does not necessarily mean that there was nothing behind the scenes going on with Part 2 and that Part 2 did not exploit the weaknesses of Part 1 without Part 1 actually being a part of the plan.
Personally, I'm a lot more inclined to believe that Part 1 was genuine incompetence and failure to communicate. Someone else already brought up the different radio frequencies used by SS and local cops. Then there's the issue of jurisdiction, rules of engagement and an overall lack of awareness of each other (SS probably didn't know every local cop and vice versa and could have mistaken the shooter for a local cop since he was in an area that was allegedly part of the local police's jurisdiction and outside of the SS perimeter).
I've worked on some school security details over the years, and you wouldn't believe some of the incompetence I've seen. One school I worked at spent thousands of dollars on metal detectors but situated them in a doorway that did not have electric outlets and had visitors going through metal detectors that were not even plugged in. Even worse, the county sheriff's office was the one in charge of monitoring the metal detectors, so it was a certified LEO who actually made the decision to put them there and was 100% aware that they did not work. I complained about it for years, and when I went to work somewhere else, they had still not fixed the issue. I worked for the school as an assistant, and I was just assigned security details as a sort of ad hoc "stand there and look tough" when we had programs and things like that where there might be a lot of people in the hallway, so basically the sheriff's office and principal didn't feel that I was qualified enough to make such an astute assessment that metal detectors only work if they're plugged in to electricity.
In my many years working as a chef in the big city, I worked with my fair share of rejects, gangsters, etc. 25% of the people you work with in restaurants are professionals. The other 75% are people on various forms of parole/probation, drug addicts, etc. I've seen people get stabbed at work, seen guns pulled out, witnessed too many drug deals to count, etc. At one point, I wouldn't dream of going to work without, at the very least, my Kimber pepperblaster and a few solid knives, and that's at the least. That's just how things roll in the restaurant industry.
In 2020, I transitioned to working in public schools since the restaurant industry basically collapsed. There is at least 1 armed sheriff deputy, various uniformed mall-cops and trained (unarmed) school security officers. There are metal detectors, locking doors with buzzers, etc. Yet, I have never felt as afraid to go to work as since I started working in education.
Never underestimate the stupidity and incompetence of uniformed law enforcement, especially when you have multiple agencies with multiple jurisdictions operating in the same theater of action.
As for Part 2 and the patsy, I honestly think it probably does trace back to Iran and revenge for taking out Solemeini. Now, you can take your pick of intermediaries, cui bonos, etc who connected the dots between patsy and Iran, since he doesn't exactly strike me like someone who speaks Farsi and has much knowledge of the inner workings of Iran so there probably was some sort of intermediary. But, I really don't buy into any of the sort of US deep state, corporate industrial complexes, etc being behind it.
Never fear Rome. The serpent lies coiled in Naples.