"Iran just needs to sweeten the deal for France like Saddam did. Then they'll buy it."
France would have supported the American invasion of Iraq, and sent a division of troops and a hundred aircraft to boot, had the US been willing to vouchsafe the then-existing French oil concessions in Iraq. Had the US been willing to agree that France got to keep her oil contracts after the liberation, the French would have been on board. When the US wasn't willing, the French went out and put together an alliance of Russia, Germany, Belgium, Spain, etc., against the war and made everything hell for everybody.
This time around, the Americans seem to get it, and since Lebanon the French are back in the game. France can be very helpful, so long as you give the French what they want. The more France lines up with the US for action, the more that it is clear that the US has vouchsafed the French oil concessions in Iran, this time, such that if the Iranian regime is toppled, France still keeps its oil contracts.
It's more useful to have France as an ally than as a pissed off and active diplomatic enemy. The damage to the US war effort in Iraq inflicted by the French was substantial.
Think everyone learned this time around. France included. IMHO, I believe the French didn't expect us to follow through on the threat to attack Iraq.
Maybe they made promises to Saddam? Just speculation.