It takes continuous effort/money to keep metaphorical company lights on. There is things you need to file periodically, legalities you need to comply with, also when they change in the future, just to exist.

So if the website shutdown coincides with the shutdown of a company or a division within the company, that might be why. And since a website will usually not shut down if it's turning a considerable profit to begin with, just deleting everything can often look like the best option.