Why does Laertes go to France? Is that something all young men did to get a little polish, kick up their heels, sow some wild oats? Polonius seems to think he will do so.

And he is an athelete, renowned for his prowess in many things but especially his sword. And Polonius tells Reynaldo to "let him ply his music". When he returns from France, he has incited a mob who is willing to stage a coup and make him king, showing him to be a leader of men, and charismatic one at that. And he just happens to know how to procure an unction of poison from a montebank!