How is it that no one saw the form of Gabriel in the first vision at al-Batha except the Prophet (peace be upon him), despite the greatness of his creation and the number of his wings?

Gabriel is from the unseen world, and no one sees him except for whom Allah permits it. The Prophet, peace and blessings be upon him, used to see Gabriel, while the Companions did not see him, unless he came in the form of a human. This is in accordance with the Almighty's saying: (And if We had made him an angel, We would have made him [appear as] a man, and We would have obscured for them what they are obscuring). Thus, people are unable to see an angel in his true form.