Complex sentence: His fame as an intellectual as well as a leader led to the invitation to Yemen; there he developed a multitude of policies that eventually became the basic guidelines for the religious as well as political characteristics of Yemeni Zaydism.
Split into simpler sentences: His fame as an intellectual as well as a leader of note, led to his invitation to Yemen. The efforts of al-Hadi eventually became the basic guidelines for the religious as well as political characteristics of Yemeni Zaydism.