I see this same thing now. In this case, it’s a more senior engineer and his manager taking credit for work a less senior engineer who’d left the team did.

There’s simply no advantage to crediting work to someone who’d left the team.

We love to blame those who are misfortunate. It’s called just world syndrome. It’s deeply uncomfortable to realize that this kind of thing is the norm, and justice is the exception. I’ve been extremely fortunate in my career, but not due to any special savviness of my own.