Two things that I am aware of that help explain the difference. There are now more midstream infrastructure to colllect the gas from the wells and pipe it to storage - so there are more wells able to provide gas and it is also quicker to bring the production of new wells to market because of the extensive pipeline infrastructure in place.
Second - they are able to drill and complete wells much faster now. A few years ago it might take a month to drill and complete a well, so 50 rigs could drill 600 wells a year. Now it is more like two weeks so it only requires 25 rigs to drill 600 wells per year. Half the number of rigs to drill just as many wells.