I suspect the site in question has rather less than a million hits per month, and the development staff is more a week of contractor time every couple of years

I suspect the site in question has rather less than a million hits per month, and the development staff is more a week of contractor time every couple of years than a full time team. This would make it hard to have a continuity of legacy technology devs and make it more likely that it just gets archived by a future team as that's easier than finding the appropriate expertise.