Years of experience, knowing exactly what to test for and add back to the water, big water changes, plus using water / 120lbs of 6yr cured live rock / 5 year old sump+refugium off of my old 29G that I upgraded from.
The first 30 days I did have a mini cycle and tested water quality daily, but since I used well cured rock that had all the right bacteria and a well established refugium with lots of pods, it didn't take long to make my new sandbed mature. A lot of my fish I have had for years and they all moved over to the new tank at the same time as the rock. Pretty much the only new thing in the bigger tank was the sand and 1/2 of the water. On a new tank with unknown cured rock you want to give it time to establish, but since I knew everything going into the tank was well established already it makes setting up a tank go a little quicker.