They tried to do equally drastic things with Superman and Batman at the time, but didn't have the balls to go through with it. Superman died and Batman got forcibly retired. But because those two are DC's iconic bread winners, everyone knew that wouldn't be permanent. GL, who was much less an iconic bread winner than either, was expendable. And already had a tradition of other characters taking up the legacy. Just like Barry, they realized they could kill Hal off and still have a monthly GL title with some other character in the suit and ring.
But the comparison is inexact. Neither Supes nor Batman had any event pushing them past the edge of self-control as GL did. Hal was on the very edge when Coast City was destroyed. One of his closest associates (Superman) was dead. Everyone he knew and loved was dead, and there was nothing he could do to save them. He was physically broken after his battle with Mongul.
He was on the very edge when the Guardians told him "NO."
Hal didn't snap just because he was suddenly a murdering dick. He snapped for very believable reasons.
Exactly my point with Batman and Superman. DC primarily cares about them and the other characters are considered expandable. The same thing with Sue Dibny getting raped by Dr. Light a few years ago-if they had tried doing that to Lois Lane, the editorial staff would have caught a shitstorm from the fans for ever thinking of that idea. The difference is that Lois Lane is a very important character while Sue Dibny is a nobody by comparison.
Also with Hal, again I can understand Hal going over the deep end over Coast City but all of it seemed so jump-the-shark to me. It was only 4 issues until Hal went fully bad after he fought Mongul and two issues before where we were introduced to Kyle. I mean replacing Hal as GL is nothing new as DC already did that with Guy Gardner and John Stewart but the introduction of Kyle felt shoe-horned. Why didn't DC use either of those two to replace Hal again? Because neither of them were popular enough to fill Hal's role, so Kyle was primarily created as a cash grab to draw younger readers. And like I said before, how does Hal losing Coast City translate to him wanting to mess with reality in the Zero Hour again and acting like a Snidely Whiplash-esque super-villain? The answer is bad editorial decision and shitty writing.