Why did this aircraft take off in the opposite direction compared to the one used by other flights right before/after it?
It looks like the reason for the Rwy 6 departure was noise abatement. The climb gradient from 6 is not as steep as for 24. The Jeppesen charts state the requirements:



And it states that if you are unable to comply with the steeper noise abatement climb gradient for rwy 24 (583 ft climb per nautical mile), you should request 6 (300 ft climb per nautical mile). Maybe the plane was fully loaded and the captain wanted to avoid a fine.