Legal - in international water, and at the time rules on dumping in the ocean either didnt exist or were very lax.... and anyways, who was around to enforce the rules?

To re-use or sell them, you have to bring them back to the US, have autioneers, and people to scrap them. Airplane recycling now is quite profitable. Back then it was labour intensive if possible at all. An anyways, there'd be few buyers for bombers and fighter planes - if the government would let a private owner buy one at all. And not that many millionaires/billionaires at that time were also qualified pilots (Hughes and a few). Of any of the planes in that article that might have been useful an resold for any significant money, would have been the C-46s. You used to see C-46s, and C-47 Skytrains and similar medium two engined cargo planes from WWII hauling stuff and people around Africa, southeast Asia well into the 90s.

But for commercial flight, as soon as the war ended Boeing, Lockheed etc. switched over to commercial designed-as-for airliners, with greater range, fuel efficiency and passenger comfort (the Super Constellation for one) And remember, the de Haviland Comet (first get airliner) flew in 1949 - everyone knew the jet era was coming. Why would anyone want worthless prop-planes?

Having big air forces is expensive to maintain. You just won the war, you still have factories pumping out new and better planes at home, enough to see you through the next decade or two and it will cost you thousands of dollars to cargo ship or ferry carrier it home.... or the hassle of ferrying mechanics and air crews back over there to fuel, fix and fly them home.

Much easier and cheaper to dump them. The US still does this. All those HUMVEES and US gear kicking around Iraq and Afghanistan? Much cheaper to sell it to the locals than haul it back.

I am curious on the random mish-mash of planes though and what exactly they would be doing there. I know the Marshall Islands were used as staging for later campaigns like Palau. That would explain the B-26s and the F-4s... but the TBFs and SPDs were carrier aircraft. Maybe these were spares from some carrier wings? Did the USN ever operate extensive patrols from land bases?

edit: I guess I didn't really answer your question, why dump it in the ocean? If its on dry land it could potentially be used by someone if they're willing to go to the effort. Could blow it up with a bomb, but bombs are also expensive.

just found this from here as well. makes sense.

The practice was very widespread and began, IIRC, back in 1944. With budget restraints, the Navy was capped at 35,000 aircraft. However, factories were producing planes faster than they were being lost. While measures were put into action to reduce production, they took some time to take effect. As a result, to meet the cap, Admiral King declared that damaged planes and war-weary ones were to be dumped overboard. This allowed the USN to keep the newly produced planes at the expense of the older ones. Going from memory here, so I want to double check this. But it was in "Fast Carriers: The Forging of an Air Navy" by Clark G. Reynolds.

and another one in that thread also points out you don't want all this cheap military gear coming home and bottoming out the market domestically. Why buy a new pickup truck when I can get a used army truck for $100? The auto makers would have a fit.