2:11 “And when it is said to them: Do not make mischief on the earth, they say: We are only peacemakers”.
This verse is still talking about the hypocrites. “Do not make mischief on the earth”,that is disbelief & acts of disobedience. Whoever disobeys Allah on the earth, or commands that Allah be disobeyed, he has committed mischief on the earth. And similarly, peace on both the earth and in the heavens is ensured and earned through obedience to Allah. If the hypocrites remain disbelievers rather than pretending to be Muslims, the evil that results from them would be less. Even better, if the hypocrites become sincere with Allah and make they sayings conform to their deeds, they will gain success.
2:12 “Verily, they are the ones who make mischief, but they perceive not”.
This verse means the hypocrites’ behavior and their claim for peace is itself mischief,although they do not see it to be mischief.
2:13 “And when it is said to them: Believe as the people believe, They say: Shall we believe as the fools have believed. Verily, they are the fools, but they do not know”.
“Believe as the people believe” means believe as the believers believe in Allah, His angels, His Books, His Messengers, etc.
“Shall we believe as the fools have believed” they meant ‘may Allah curse the Companions of the Messenger of Allah’ SAW. “The fool” is the ignorant, simple-minded person who has little knowledge in areas of benefit and harm. Then Allah defended the believers Himself, and answered the hypocrites by saying “Verily, they are the fools”.
“But they know not” they are so thoroughly ignorant and unaware of their degree of deviation,which is a severer case of blindness.