Explanation 1: "Drone shows" are a thing. They use Real-Time Kinematic (RTK) GPS to guide hundreds or thousands of drones over a preset pattern. RTK GPS relies on two inputs: the satellites, and a precisely-located base station to correct errors in the satellite data. If Explanation 1 is true, the Iranians bought a drone show system from a Chinese company, tore the drones down, and retrofitted the guidance systems into armed Iranian-made drones. Iran has a fairly decent defense industry, or at least they did before Trump started dropping bombs on their country.
Explanation 2: There's at least one drone show contractor in Iran. This individual either conducted a drone show on his own accord or he was hired by an Iranian city to do one, in either case to make the locals happy. (They have been getting Trump's bombs and missiles dropped on them for months. They could use a morale boost.) The F-15 pilot saw this, freaked the fuck out and let his jet go out of control. The "jellyfish" thing is what suggests to me this is what happened - a "jellyfish" formation makes no tactical sense but it'd look really cool, and "looking really cool" is the whole point of drone shows.
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