This is entirely my personal perception of the matter, but when DT joined RR, it seemed they had a "plan" with DT, and that plan was to go metal, and by extension, go big. That's what RR signs, it's what they do.So, the hair got long, dyed black, and it was all leather jackets and gritty promo pics.
But, in the end DT is DT, and TA was an assertion of what they are about, which is "dare, or go home". Tour-wise it didn't work out, we all know that.
In my mind, that's probably how this long IAW tour came about, as an attempt to revitalize the base, and please RoadRunner at the same time.
However, I think we all know that there is a huge difference between the number of people who show up for "IAW Live" versus "Best of DT12 and TA". As kingshmegland's friend so poignantly said before the Boston gig "two new album songs, max. Nobody wants to hear that stuff!"
From that realization I think all parties probably said "let's part here, and we'll move to a label that specializes in smaller, dedicated fans bases". I am very happy with that development, I think a less hamstrung DT will make for better music.
To reiterate, all just personal hunch and theories.