Posted by: Onomatopoeia
These Elites are most likely Covenant fanboys and are doing -blam!- to honor Truth. Thel wouldn't go back to war unless he found out about Oni supporting one of his enemies or if the UNSC attacked Sanghelios.
If this is not the case then;
A) Thel lost in a duel.
b) He's a political prisoner.
C) Covenant 2
It is quite possible a new leader is in power. In the end of glasslands, remember that the last thing Dr. Evan Phillips,( or Phillys), saw was a white flash then !Boom!, gone.