How can you explain the multinational composition of Napoleon’s army?

This fact can be explained by the fact that Napoleon conquered the lands of Europe for a long time, after which the troops of the occupied countries joined the ranks of his army. Thus, the army of the French emperor became multinational. True, despite this, the French were still the most combat-ready unit. It was they who made up the bulk of his guard, which was the most combat-ready and experienced in his army.