The Sutra of the Imam is also a Sutra for those who are behind him

Narrated Ibn `Umar:

Whenever Allah's Messenger (ﷺ) came out on `Id day, he used to order that a Harba [??] (a short spear) to be planted in front of him (as a Sutra for his prayer) and then he used to pray facing it with the people behind him and used to do the same while on a journey. After the Prophet (ﷺ) , this practice was adopted by the Muslim rulers (who followed his traditions).