Why did king john sign the magna carta?

Literally did an idiotic thing which limited his power. he was very unpopular with the people and especially the barons.. thats why. he was forced

King John's people did not like him very much. They wanted to limit his power, so they made the Magna Carta, which limited the king's power. One thing that it did was that it made the king have to obey the law, just like all of the nobles, vassals, and peasants under him. Formerly, he was above the law. Of course, no king would ever agree to this, and King John was no different. The only problem was the threat of a civil war. Therefore, he was forced to sign the Magna Carta in 1215.

Ghana, first of the great medieval trading empires of western africa (fl. 7th–13th century). it was situated between the sahara and the headwaters of the sénégal and niger rivers, in an area that now comprises southeastern mauritania and part of mali.