If the cause was a pilot that was suicidal than either this was a spur of the moment act or preplanned. In a spur of the moment scenario he pulls a flight 800 and goes right in and we would know about it. In a planned scenario he either goes out in a blaze of glory or dies quietly. Since he did not crash the plane in a spectacular manner that leave picking a location as far away as possible over the deepest part of the ocean to lesson the chance of being found and ditching the plane. Considering the range of the aircraft and last satellite position I would guess he put it in the Diamentina Trench, or better yet the Diamentina Deep. At its great depth the pinger would almost be impossible to pick up before its battery dies.
Maybe he’s just an entrepreneur and is simply setting up his retirement fund in a big way.