good questions but you will never get any clear answer on that because there is too much at stake.
Never mind, there were cheap and effective drugs available that were more effective anyway, but emergency approval for a vaccine required that there was no alternatives available. Hence The demonization of anything other than the vaccine.
I'm not saying fluvoxamine is bad or anything. By all means use it if you lack access to the vaccine. The FDA isn't dictating what Brazil can do. The point of the vaccine was to get us to a place where we can go back to our normal lives while avoiding the usual catastrophic circumstances that accompany a pandemic.