The upkeep was apparently 12 engineers and they had tens of millions of users. It doesn't take that many users to justify 12 engineers plus infra, so it sounds like it was more that Google doesn't care to operate any product unless it will have users in the hundreds of millions.
By the end it had an upkeep of one dude's 20% time. It was very reliable and the Google infrastructure didn't require much ongoing maintenance at that time, the servers just kept on trucking.
Having basically all their users (well, as much as for any of their revenue generating products anyway) be revenue generating would require practically no effort for google specifically.
It fit their revenue model perfectly. It is trivial to put the exact same ads in there as they already had on search and gmail, and it is stickier than search or gmail.
LOL. the Googs worrying about being rude is charmingly funny in a webcomic kind of way. they removed their tag line of don't be evil. you think they are concerned about being rude?
however, this is precisely what Reddit was complaining about 3rd party apps doing to their content. everyone was trying to pivot to blaming AI scrappers, but that's just FUD.