What is the wisdom behind the the obligation to recite Surat Al-Fatihah in every prayer and its being considered an essential pillar without which the prayer is invalid?

It is not befitting to ask, "Why did Allah choose?" because Allah is not questioned about what He does, but rather, one inquires about the wisdom behind it. Al-Fatihah is the greatest surah in the Qur'an, the Mother of the Book, and the Grand Qur'an because it encompasses praise for Allah, commands for worship and sincerity, an acknowledgment of human weakness without His aid, and supplication to Him for guidance and sufficiency against the ways of those who renege. The Qur'an does not deviate from these objectives.