Delhi was heart for Indians because all the rulers who ruled entire India made Delhi their capital.
Revolt of 1857 shows the same as it was operated from Delhi with the help of Bahdur Shah Zafar (last Mughal emperor), so British feared that if they shift their capital to Delhi they will evoke the sentiments of Indians. Most important of all was strong nationalism that emerged in Bengal. Legacy started by Raja Ram Mohan Roy was carried forward by Aurobindo Gose, Rabindranath Tagore, Khudiram Bose, Ashwini Kumar Dutt, Subhash chandra Bose etc. Furious revolutionary activities were conducted, of which Bombay and Madras Presidency was also sunk in Nationalism. And this compelled British to shift their administration to Delhi.
Delhi became the Capital of India in the year 1911 when King George V was crowned in England. The areas around the Yamuna had always been special for the Mughals and so was the city of Delhi. The Mughal Emperor Bahdur Shah Zafar used to live at the Red Fort in Delhi during the mid-19th century. The political movement in Delhi marks significance as the revolt ended up changing the swing of the people and acting as an igniter so the British were aware of the symbolic importance of Delhi.
The British wanted Delhi to forget its Mughal past. Thus various spectacular events were organized well before 1911. The British realized during the revolt that Mughal emperor was still important to the people and they saw him as a leader, thus such functions became important to show their power. Thus I the year 1911, when King George V was crowned in England a Durbar was held in Delhi and the decision was announced at this Durbar.
Earlier Jama Masjid used to be the highest place in Delhi, but after then British importance was to be asserted thus Viceroy’s Palace i.e. Rashtrapati Bhawan on Raisina Hills was higher than Shah Jahan’s Jama Masjid. It took 20 long years for New Delhi to be built up and it was designed by Sir Edward Lutyens and Sir Herbert Baker.
And hence Delhi Assembly after the Rule of British was gradually constituted on 7 March 1952, after Independence under the government of Part C States Act, 1951 and the first council of ministers was led by Chaudhary Brahm Prakash who became First Chief Minister of Delhi. However the first sitting of the Legislative Council was held at the Chamber at Old Secretariat on 27th January, 1913.
Delhi was chosen as the capital because of its old traditions of Hindu-Muslim unity, also due to its strategic and geographical location and as a seat of culture.