As much as I disliked the LoS trilogy (except the very first game which had potential) I don't think Cox is to blame for IGA "losing his castle". MercurySteam pitched their project and Konami was impressed. We really have no idea what the other pitches looked like and we definitely don't know in what shape IGAs "Alucardvania" was. The teaser trailer from a few years back looked - dare I say it - very lackluster. The graphics were Dreamcast era.
In addition to that, IGA had recently made Judgment - a universally panned fighter. And Harmony of Despair - a hodgepodge of recycled assets. Lords of Shadow really came off as a fresh thing and I'm not surprised IGA lost his job.
I don't think you're someone with an agenda against IGA or anything Shel-kun, but what you're writing here is a bit revisionist in my opinion. Not that I blame anyone for thinking that way since before we didn't know what happned, but recently there was an interesting interview with IGA that shed some light on his period as Castlevania producer.
Anyway, what IGA basically said was that after SotN was finished he and the team wanted to take a break from making that kind of game because they were a bit burned out creatively. So during that time the series got handed over to KCEN and KCEK while IGA produced another game called Elder Gate. Around 2001 IGA really wanted to be involved with the series again so he begged his boss to be once again assigned to the series. They said it was alright but under the condition that IGA
had to produce a CV game every year from that point on. In the interview IGA even said he basically had to compress a 3 year development cycle into 1, but he didn't care because he loved working on the series so much.
Initially his games peformed well (they were actually making a profit), but later, he said, the prices of (handheld)games were going down (I didn't check this, but maybe someone else know more about this) and the fanbase wasn't increasing enough to compensate for the losses (IGA said fanbases can increase a little bit but never actually double). This is why they tried cutting corners like recycling sprites, something IGA always gets crap for. But this ended up only decreasing the costs around 10%.
So eventually he started working on that PS3/Xbox360 game, but the game didn't really came together properly. IGA said it was because of this and the series making less of a profit that they decided to do the whole pitch thing. IGA's game ended up being compared to MercurySteam's game and we all know what happend afterwards. IGA was then already asked to step down as producer, only being allowed to do minor projects (and I assume finishing up OoE). So I don't think games like Judgment and Hodespair even factor into the decesion to remove IGA from the series. He really just got screwed over by both Konami and game retailers. Anyway, that's the story through my own personal filter. You can check out the interview on YouTube. It's by Kinda Funny games, around one hour into the video.