A movement that starts from the bottom up rather than top down is called what

A movement that starts from the bottom up rather than top down is called grassroots.

Explanation:

All successful movements are started from bottom level people, if movement need attention it must be supported by middle class people but that movement need continuous support it must be supported by the downtrodden people. Gandhiji started the national movement from grassroot level through Champaran Sathyagraha in Northern Bihar. Because downtrodden people stood with the movement rather than top - and middle-class people. Gandhiji need the administration and power distributed from bottom to top level rather than present structure.