The game being P2W doesn't have much to do with Kim Hakkyu. Granado Espada and Tree of Savior aren't exactly less P2W.
Kim Hakkyu probably wouldn't have allowed for RO to become as unbalanced as it became after episode 10ish, though. Renewal probably wouldn't have happened either. He's pretty good in game design, but I don't think he's very good in regards to marketing.
It's also not only Kim Hakkyu. A lot of the original developers left Gravity and joined Kim Hakkyu. It gets pretty obvious when you reverse engineer the server source code, because then you see how developers desperatively tried to fix skills with "bandaids", obviously not understanding how the existing code works (as they haven't written it).
Also I highly doubt that the Aegis files leaking really hurt Ragnarok Online in the long run. The leaks are what eventually formed the community, all the DB websites where you can look up stuff for example. Being able to know the drops rates and spawn rates and how all the mechanics work in detail up to the line in the source code strongly helped with all the guides. This is a luxury other MMORPGs never offer.
I'd go so far and say that the strong community formed around Ragnarok Online is what kept the game alive still 18 years later. While many other MMORPGs that never had any leaks and probably had less bugs, better controls and a fixed development team died.
@Kolby
eAthena is just based on jAthena and jAthena mostly got their data from packet capturing not from leaks. Of course there were some leaks, most notably the database files that are just lying around on the server and can be read by everyone. This helped to get exact drop rates, monster stats and spawn rates. Most of everything else was just a community effort. People actually went on official server, moved to all the NPCs, noted down there coordinates, wrote down the dialogues, etc.
There were even bots that teleported around just to count monsters for maps there weren't any leaks for, so we could conclude spawn rates.
The only true leak is the official Aegis emulator, which also resulted in several private server, especially early on, before eAthena got popular (long time after Kim Hakkyu already left). Of course Aegis is also used to run tests to figure out how things work. And it allows reverse engineering too, though only few people are capable of doing that.
I probably know a lot of Ragnarok Online fun facts, but it's hard to just grab them from my memory. I'm better at answering direct questions.