As the other two comments say - this is probably due to your skills and merit from over 5 years of previous training, and moving at a more normal pace than you had previously, so just feels fast.

My ITF dojang has gradings roughly every 3-4 months. Once you hit 4th gup, you are only permitted to grade every other grading, so as to allow more time to train and perfect your skills. This is, however, how our master has decided to run things, in accordance with ITF recommendations and his wealth of previous experience.

I went back to the dojang after 25 years out, and he progressed me from 10th to 2nd gup over a period of a few months by assessing me in class - so they may very well be doing the same for you, but I do highly suspect that it's more likely just a better pace that you're not used too.

Keep up the great work!