Musk is claiming millions are in a database with a certain switch set a certain way. He is insinuating that people who allegedly at 120+ are receiving checks, but didn't actually say it.
That is intentional! Of course, Musk has always been big on baseless hype and insinuations.
And when you read the article you can see that they might legitimately be paying benefits based on a 120 year old's record. If their widow never remarried the widow will receive the same benefits the person would have, thus the record must remain active and paying even though the person is dead. It's a logical consequence of how the system operates that most people simply don't think of.
And I'll add: he doesn't think. I suspect incompetence more than malice. He thinks there's great fraud and thinks he's found it when he finds anything he doesn't understand.