The sort of loneliness that impacts life negatively is probably more of a mental space than a physical one. While Mandela was isolated, he was not without cause or without allies even if he was physically separated from them.

If you're on a purposeful mission you can endure a lot of destitution. The loneliness that is making the news is more of a secular malaise. People without purpose, task, meaningful communities to be part of, and so on. They might not even be literally lonely in a physical sense.