Diversion?
The only possible terrorism angle I can see is a pilot infuriated with the political situation in his own country decides to turn the plane around and head back to the city he left from — with bad intentions. It does appear he was very upset with recent developments in his own country. Maybe the “plan” met resistance and didn’t work out as intended.
Look where I want you to look, not where I don't want you to look.
Sure, could be a smaller part of something else entirely.