The French foreign legion are not mercenaries, they are soldiers fully in support of the French colonial project (many of them unfortunately are subjects of French colonialism as well) who are looking to gain French citizenship through military service. This is important because if they were simply mercenaries then Russia could attack them without thinking about it. That is not the case here, these are French troops wearing the French flag engaging in offensive operations under direction of the French president. This is a big step even though it’s a small number of troops. They are being sent to Ukraine because these troops were pushed out of Africa which is where France gets most of their uranium for their energy security. That is partially the reason France outspoken about sending troops.