He explains this in the article. Two children are in Germany with their mother, and the other children are still in high school or college. He hid his homelessness from all of them.
As a father, to be unable to support yourself, let alone your kids, can be a destructive blow not only to your self-respect, but to your children's respect for you. I suspect that that's what he was trying to avoid, and I find it wholly reasonable. His children's respect might never return, and it's clear from the article that his relationship with his children is part of what he valued most.
If it was easy to avoid the situation, he would have.