Why is he represented with a chair?

12th July 1789, Camille Desmoulins comes back from Versailles. He has just learnt that Necker was dismissed. To announce the news to people, he gets out of the Café of Foy, situated in Richelieustreet in Paris, gets up on a chair and harangues the crowd. From this chair he picks up a leaf from a chestnut tree, then places it on his hat, and invites everybody to imitate him. And so is born the first revolutionary cockade...

Here is the statue located in front of the Royal Palace which inspired the creators. Do not look for it, it was destroyed in 1941 by the German army.

The revolt chair