But that feels more complicated than...
Yes, it
does feel more complicated than a narrative that seems on its surface to check all the boxes. But life often (probably more often than not)
is more complicated than that. Occam's razor is a useful rhetorical tool for dissecting arguments to determine where the weaknesses are. But although it is tempting to apply rhetorical tools like that to messy human interactions and other aspects of real life events, that misapplication is unwise and often just leads to people drawing conclusions that are later shown to be incorrect.
To put "what most likely happened" in my own words, here are what seems to me to be the most likely scenarios (in VERY general terms):
1. The rest of the band decided first of all that they wanted to reunite with Mike Portnoy, and then decided to part ways with Mike Mangini
because of (the two most important words) the decision to reunite with Portnoy. OR...
2. Mike Mangini decided he wanted to leave, and the timing was such that it worked out for the band to decide to reunite with Mike Portnoy. OR...
3. The decision was initiated by the band, or was mutual, for some other reasons I haven't thought of, and the timing was such that it worked out for the band to decide to reunite with Mike Portnoy.
I still don't have any facts suggesting that one or the other is more likely true, so if pressed, while I think "I don't know" is still the most correct answer, my opinion of the odds of each one would be about:
1. 45%
2. 45%
3. 10% (just because I don't know what this could be)
It seems like a LOT of people are all in on #1, which I don't really get. But that's your prerogative if you fall into that category.