[Protecting the Caliph and Caliphate] The Turkish Ottoman Empire joined World War 1 on the side of Germany and suffered military defeat against the Britain and her allies. After the war was finished, UK and USA seemed determined to overthrow the Caliph and divide the empire into different territories. Protecting the Caliph was very important for the Muslims because he was the symbolic religious and political leader of all Muslims in the world. Similarly, the disintegration of caliphate would harm the concept of Muslim Ummah. So, the Khilafat Movement was launched in November 1919 by Maulana Muhammad Ali Jauhar and his brother in order to protect the caliphate from breakage and save the Caliph from being dethroned.
[Holy Places] The Ottoman Empire contained the Holy places of Arabia. The Muslims of India feared that collapse of the Caliphate could result in fall of the Holy places under the control of non-Muslims. Muslims all over the world have strong religious attachment with these places and their sanctity is of topmost priority to them. Therefore, the movement was launched to defend Turkey and the sacred places.
[British Actions] During World War I, Indians were supporting the British against Germany. When Turkish Empire joined the war on the side of Germany, Indian Muslims came in a very awkward position because it was very difficult for them to fight against their Muslim brothers. The British realized the situations and put a number of prominent Muslim leaders behind the bars, which obviously offended their feelings. Secondly, the British prime minister had given assurances that Turkey would be protected, but later on the allied powers changed their mind and decided to remove the Caliph. These actions were convincing the Indian Muslims to launch massive protests against the British Government in the shape of Khilafat Movement.