According to the article, Valve is in fact currently maintaining all those features with a team of ~80 people. So this is a good opportunity to improve your understanding of the number of people it takes to maintain software.

One thing Valve seems to understand better than most big tech companies is that once a product/feature is done, you don't need the same size team to maintain it. A lot of parts of Steam have been functionally unchanged for the last few years and just... keep working. The people who worked on Cloud Saves have presumably moved on to something else, instead of entering a Google-esque cycle of pointless Cloud Saves feature launches and deprecations.