The Hal we see in 2026 isn't Hal.
Everyone is focused on WHO killed Hal Jordan. I think we're asking the wrong question.
Episode 1 goes out of its way to establish that some aliens can perfectly imitate humans. Then we get a corpse with NO ring.
What if John didn't find a dead Hal?
What if he found something that was wearing Hal's face? And the real Hal is somewhere else.