They never officially revealed why the change, but the new Maxx replaces both the old Maxx and the old ultra. I'm sure that part of the reason was to reduce the cost of the phone, and, since they were removing the ultra, to reduce the number of skus that they carry without losing the people who don't need 32gb of storage. The phone was out 9 or 10 months when they made the change, and all major OEMs had new models of their phone by then, so I'm verizon figured that everybody looking for top of the line specs was looking elsewhere right now.
It's not a better phone. Everything's the same except the amount of storage and the casing.
The phone has been able to do xlte since last November, well before Verizon started calling it xlte. It's just band 4, which was added with the early November jellybean ota on the original Maxx, ultra, and mini.