What is the meaning of Aqeedah, and why do scholars focus on it more than other matters such as Hadith and Fiqh?

Creed (Aqeedah) is that upon which a person binds his heart and believes with firm faith, adopting it as a doctrine and a religion. If this faith is sound, then the creed is sound; and if it is false, then the creed is false. In Islamic terminology, "Aqeedah" encompasses every creed, whether true or false, and signifies faith and firm conviction. As for the Islamic creed, it means firm conviction, submission, and faith in Allah, His angels, His books, His messengers, the Last Day, and divine decree (Qadar), as well as the pillars of Islam and other definitive matters of the religion. Sometimes, the early generations (Salaf) used other names for the science of Aqeedah, such as: Tawhid (Monotheism), Sunnah (Tradition), Usul al-Din (Foundations of Religion), Al-Fiqh al-Akbar (The Greater Jurisprudence), and Ash-Sharia (The Law). All these names indicate the importance of this science and its high status in Islamic law. It is the foundation of the prophets' call, and upon it actions are accepted or rejected, which makes it worthy of attention and focus in learning and teaching.