Why do the Tarawih prayers in the Grand Mosque and the Prophet's Mosque differ from the Sunnah, and why do they pray 20 rak'ahs instead of 11?

A Muslim should not allow matters of ijtihad (independent reasoning), where differences of opinion are permissible, to become a cause for division and conflict, such as the number of rak'ahs in Tarawih prayer. Two groups have become extreme in this regard: the first denied any increase beyond eleven rak'ahs, and the second denied restricting it to that number. The Prophet, peace and blessings be upon him, did not specify a particular number of rak'ahs for night prayers. The majority of scholars from the four madhhabs (schools of thought) permit an increase beyond eleven rak'ahs. Therefore, whoever prays eleven rak'ahs or more has done well, and neither of the two groups should be denounced.