From what I can see (and have not analysed in depth), KL/AF are driving up load factors by keeping their fares relatively low (and their fuel surcharges don't seem to be as punitive as LH/LX/OS/SN). So they appear to be running quite high load factors, but I'd be betting their yields aren't great.
KL/AF have the benefit of tremendous heritage at BRS. Their route-network is expansive and well understood, and certainly the bank arrangements at AMS work very well. (Personally, I wouldn't connect through CDG until it was the very last option). So they have the front-of-mind awareness and the volume of business.
It's possible that what KL/AF has now represents the upper limit of passenger volumes on full-service airlines from BRS, and that there's no growth left in that market. I hope that's not the case.
It would be disappointing to be in a situation where point-to-point airlines account for nearly all movements at BRS, and the only credible long-haul connecting option is KL through AMS.
(And honestly, while we're at it, the SN marketing of the BRU route is just painful. Do they run the same "cut out the Chunnel" line in NCL as well? Awful).