Question

why did mahatma gandhi feel the need to launch a broad based movement in 1920

Answer 1

1) While the Rowlatt Satyagraha had been a widespread movement, it was still limited mostly to cities and towns. Mahatma Gandhi now felt the need to launch a more broad-based movement in India.
2) He wanted this movement to spread even in villages and remote areas.
3) For the nationalist movement to be successful, members of various religions and castes had to be brought into the movement.