Narrated Zaid bin Thabit: Allah's Messenger (ﷺ) made a small room (with a palm leaf mat). Allah's Messenger (ﷺ) came out (of his house) and prayed in it. Some men came and joined him in his prayer. Then again the next night they came for the prayer, but Allah's Messenger (ﷺ) delayed and did not come out to them. So they raised their voices and knocked the door with small stones (to draw his attention). He came out to them in a state of anger, saying, "You are still insisting (on your deed, i.e. Tarawih prayer in the mosque) that I thought that this prayer (Tarawih) might become obligatory on you. So you people, offer this prayer at your homes, for the best prayer of a person is the one which he offers at home, except the compulsory (congregational) prayer."
Sahih al-Bukhari
Book 78, Hadith 140 http://sunnah.com/bukhari/78/140
Narrated Zaid bin Thabit: The Prophet (ﷺ) took a room made of date palm leaves mats in the mosque. Allah's Messenger (ﷺ) prayed in it for a few nights till the people gathered (to pray the night prayer (Tarawih) (behind him.) Then on the 4th night the people did not hear his voice and they thought he had slept, so some of them started humming in order that he might come out. The Prophet (ﷺ) then said, "You continued doing what I saw you doing till I was afraid that this (Tarawih prayer) might be enjoined on you, and if it were enjoined on you, you would not continue performing it. Therefore, O people! Perform your prayers at your homes, for the best prayer of a person is what is performed at his home except the compulsory congregational) prayer." (See Hadith No. 229,Vol. 3) (See Hadith No. 134, Vol. 8)
Sahih al-Bukhari
Book 96, Hadith 21 http://sunnah.com/bukhari/96/21
So the question is, whose sunnah is being followed when tarawih is prayed in congregation at mosques?