Some interesting points here. Added to the mix could be something as simple as they waited until the last possible moment to intervene - 'look fellas, we've been watching this nonsense going on and on and now you've brought it to our doorstep. That's not on, lads; we've had enough and it stops now.' Their ' red line' had been crossed and they decided now was the time to act. I love the absolute calmness of the Organians. John Abbott did a great job.
The Organians' "red line" was evidently the convergence of the Klingon and Federation fleets.
However, the Organians did allow members on either side to get hurt or killed in the lead-up to the major confrontation. For example, the Enterprise
blew up a Klingon vessel in the teaser.