The aircraft appear to have become "stuck" to each other perhaps due to aerodynamic forces similar to how a piece of paper gets stuck to a car windshield (probably something to do with one of the Bernoullis). There wasn't much of an impact to cause a destructive event such as compressor stall. Perhaps the pilots were waiting to see if the aircraft would become un-stuck, or to get clear airspace into which they could eject?
I actually looks like the vertical stabilizer of the lower plane got lodged into the fuselage of the other.
That’s my read as well, but I’m looking forward for an official analysis as things often aren’t as they appear.