From my reading, it seems that Petain was very keen, almost eager, to sign the armistice and set up a pro-German government. It just seems so strange from a man who was a beloved war hero. Why did Petain and his supporters push the armistice so strongly, and not consider fighting on from the colonies? Was it a simple lust for power, or was it more complicated than that?
You have to understand that in 1940 the French were utterly defeated, a few such as DeGaulle wanted to continue fighting but the vast majority of the French were crushed and wanted to end the fighting. The French prime minister Paul Reynaud stepped down and made Petain his successor. Both Petain and Weygand (French commander) considered the military situation hopeless and Weygand was angry at the British because he though they hadn't pulled their weight and left France to fend for itself. Petain had been calling for an armistice for a while. Petain first and foremost was a patriot who wanted France to survive; he didn't want all of mainland France to suffer while the French fought on from the colonies, they had no idea that the terms the Germans would impose on them at Compiègne would be so harsh. At the time of the armistice many assumed Germany would quickly deal with Britain and that resistance would be pointless. The French resistance didn't really become dangerous until the war started to turn against Germany.
Its also worth noting that Petain was really a figure head in the Vichy regime and that Pierre Laval and before that Francois Darlan held the real power and, Pierre Laval moved the country more towards collaboration where as Petain wanted to try and avoid collaboration.
Sources:
The Second World War: John Keegan
Vichy France: Old Guard and New Order, 1940-1944: Robert Paxton
France: The Dark Years, 1940-1944: Julian Jackson