How did the monarchy get stronger in France?

By making sure that the only way to advancement and fortunes was by living permanently at the court; thereby effectively removing the nobles from their estates and power bases and moving them to a central place where an eye could be kept on them. Richelieu further saw to it that all those valuable offices to be given out were no longer either hereditary or in someone else's gift, but were only for the king to hand out for life or for a specific period.