I find it surprising and disturbing that those three F-5s weren't intercepted and shot down.
I find it to be expected.
The Iranians successfully mounted ultra-low-level attacks more than once during the Iran-Iraq war. There was--and is--no reason to think that they couldn't do it again.
Nonetheless, the US neither hardened its forward operating bases nor provided adequate defenses against low-altitude, low-tech attacks. Why not? Most likely because fortifications, Stingers, and automatic AA guns:
a. are not sexy/expensive enough to get the Pentagon/White House/Congressional blood pumping
b. are not profitable enough to attract our defense industry/monopoly
c. divert funds that could cover at least some of the cost overruns on projects that better address (a) and (b).
As a whole, the US military bureaucracy has long had a firmly embedded and foolish belief that the side with the most advanced technology will win
every time and that the unexpected
never happens. We build gold-plated systems designed and optimized for Air/Sea/Land/Space Dominance in some hypothetical future war against one or two hypothetically equal opponents. Real-world experience fighting resilient, low-tech opponents counts for little. The politicians, defense CEOs, and armed services bureaucrats all prefer the glitzier, top-dollar Future of War projected by animated AI-simulations, one-paragraph executive summaries, and 5-bullet Powerpoint presentations.