Did you read the Reuters article? It answered those questions for me, too. Countries were asked if they want to commit to purchases before the vaccines were even approved.
So they committed to enough purchases that even if they were not all approved, they would still be able to take care of their people.
They agreed that if they ended up with more than they needed, the rest would go to countries that could not afford to commit to the purchases.
So it is not a case of "taking more than needed.' They were asked to commit before the vaccines were approved. They handled it the best possible way. Instead of not taking enough, they made sure to take care of their people, with provision for helping others, too.