All praise and thanks belong to Allah, the Lord of all that exists. May the peace and blessings of Allah be upon the Noble Prophet Muhammad ﷺ. To proceed:
On the authority of Mutee' Bin Al Hakm (radi Allahu 'anhu) that the Prophet ﷺ used to ascend the Minbar and we faced him (while he delivered the khutbah). [Saheeh, As-Saheehah: 2080]
Imaam Al Bukhaaree narrated this Hadeeth under the chapter heading: "The people facing the Imaam, the people facing the Imaam while he delivered the Khutbah, and Ibn 'Umar and Anas(radi Allahu 'anhumm) used to face the Imaam," then he narrated the Hadeeth of Abee Sa'eed (radi Allahu 'anhu).
Al Haafith Ibn Hajar (rahimahullah) said,
The Author (i.e. Imaam Bukhaaree) extracted from the Hadeeth that which was intended by the chapter heading. The reference point of proof (extracted from this text) is that they (the Sahaabah) used to sit in front of the Prophet ﷺ in order to hear his speech which necessitates that for the most part they were looking at him; this however, doesnot obscure that which has preceded from the fact he stood during the Khutbah. This is based on the fact that he would deliver lessons while sitting on an elevated place with them sitting beneath him (and facing him). If this was the case outside of the Khutbah, (that they would sit facing him), during the Khutbah would then take precedence due to the evidences which obligate (the congregant) to listen to the Khutbah while remaining silent (1).
The wisdom in facing the Imaam is because this posture is most suitable for listening to the speech and exhibiting good behavior toward the Imaam. Facing the Imaam with your body, heart, and mind is more conducive for understanding the sermon and in compliance with the establishment of fulfilling and attaining the purpose for which facing (the Imaam during the Khutbah) was legislated.
(1) Fathul Baaree [2/402]