That maneuver they were attempting looks WILD. Would have been amazing to have pulled of. Or, perhaps to have regularly pulled off until today. I'm guessing that must be some sort of vectored thrust trickery.
I don't think anything after the second jet's merge was deliberate. NASA's HARV is the only F/A-18 with a thrust vectoring exhaust designed for it, and it's doubtful that similar kit would go on an EW jet.
What's shown in the video appears to be some form of slipstreaming by the chase craft that causes them both to lose pitch authority, pulling up into a stall state and then a yaw tailslide.
Cue the development of a limpet drone that would be enough to take down one of these birds in a non-destructive way… although perhaps these ones in particular would be uniquely positioned to deal with such adversaries.
The video, apart from the apparent loss of situation awareness by the following pilot, seems to show the leader making an aggressive left turn basically into the path of the other aircraft. I'm four hundred miles or so from the location but we've had some weird weather here today, and I've heard it was even more weird in Idaho. Reports of high wind speeds and gusts. I wondered if the lead aircraft had been hit by some sort of atmospheric event that pushed it into the path of the other when it happened to be too close to correct.
What's shown in the video appears to be some form of slipstreaming by the chase craft that causes them both to lose pitch authority, pulling up into a stall state and then a yaw tailslide.