The other things are conjecture on my part.
Mike wanted to be heavier with DT. James voice didn't fit that style he had envisioned. Hence he started to add his lead vocals.
Mike's focus on side projects that influenced him with DT. He also became tired of his "first wife, DT."
So the other music was alluring. Add he wanted the break because of these influences and the rest of the band didn't.
I thought that was all basically assumed to some degree.
To a degree the second/third point is true. MP has stated in interviews that (in essence) he noticed how much fun he was having with these side projects and with A7X, in comparison to the time spent when touring with DT. So he wanted to take a break so that the band could recharge its batteries and feel reinvigorated, instead of just plodding along - absence makes the heart grow fonder, as has been proven true by him and JP getting together around the holidays and finally doing something musically.
To the first point, I have to disagree. While MP may have been the most "metal" guy in the band, that didn't mean that JP wasn't in full agreement with it. Everyone's super quick to point to SC and BCaSL as being "metal" albums, but there are a lot of non-metal elements to parts of those albums, too. If they had done back-to-back albums that were like ToT, I'd be more likely to agree, but that's not the case.
Regarding MP adding his vocals, I think you forget that he (and JP) started adding their vocals back on FII, and MP's first featured prominently on SDoIT which is probably one of the most diverse albums in terms of styles. Even after World Tourbulence, they had the big talk with JL, and back then there was the talk that maybe his style of vocal wasn't exactly what they wanted, but chose to continue on with him, if he would make improvements on his performances, which he did.
So this is nothing new and wasn't something that just cropped up within the last 1 or 2 years that MP was still in the band.
BTW, kingshmegland, I am wondering if your unnamed source is getting the split between MP and DT mixed up with the split between Geoff Tate and Queensryche, which has been confirmed that they had security guards to separate Tater from the rest of the band. That seems to be the most logical possibility.