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?
That’s my read as well, but I’m looking forward for an official analysis as things often aren’t as they appear.
I actually looks like the vertical stabilizer of the lower plane got lodged into the fuselage of the other.