Why did Gandhi launch the Salt Satyagraha in 1930 and with what results?

After withdrawal of the non-cooperation movement by Gandhi after Chauri-Chaura incident in 1922, there was no large-scale mass movement.

After Lahore Session of Congress 1929, Gandhi presented his eleven points demand which did not receive positive response. The Congress Working Committee gave him full powers to launch this Civil Disobedience Movement at the time and place of his choice. Considering Salt Tax as the most inhuman tax, Gandhi identified it with mass suffering which created discontent allover the country. So, Gandhi decided to launch the Salt Satyagraha in 1930. Therefore, on 12 March 1930 Gandhi, with his chosen 78 Satyagrahis, marched to Dandi and violated the salt law, thus creating a nationwide movement.

After Dandi, Salt Law was violated at other places also. Other activities like boycott of schools, colleges and government offices, burning of foreign clothes, no-tax movement and shop picketing also started as a consequence. People joined the Civil Disobedience Movement enthusiastically.