Generics new gTLD went live early 2014, and dot brands domains a few months later.
There was a big increase of delegation around April 2015, and then again around July 2015. These increases correspond to deadlines from ICANN, depending on the type of requests, of negotiations on the contract etc..
It also corresponds to the moment when the Spec 13 was accepted, after Singapore ICANN meeting in March 2014.
This shows the complexity of the process between ICANN and the major brands.
The number of TLD grows faster than the number of Second Level domains. A small number of .brand TLD actually have larger volume, but the bulk of the TLD actually have a small number of second level domains.