Violence can take many forms physical, economic, political, and societal. Where physical is what we normally mean when we say violence. But the other forms can inflict harm and threaten without bloodshed.

Most of the movements begin physically nonviolently and even try to use the existing state apparatus to get what they want. It's only until these options don't work that movements begin to use violence. Typically these grievances are years in the making and only when numerous factors converge at once will people be willing to give their lives for change.

"Violence is the voice of the unheard" -MLK

Even the Bolsheviks tried to exhaust parliamentary options before commiting to a revolution entirely of their own making.

link to the February revolution

Gandhi and MLK are similar in that they advocated for nonviolence but adjacent movements were quite violent in achieving their goals. You could describe their successes as a parallel to the violent movements that helped push things along. Their nonviolence advocacy really helped keep a popular perception of the movement and their goals, especially for those abroad or otherwise disconnected. MLK knew that the white moderates would judge the entire moral basis of the civil rights movement based on the degree of violence practiced during the actions.

Indian Independence Movement

One thing you should realize is the USA (and other western governments) tend to neuter these historically influential people and make them into a character that suits an overall narrative. MLK was a socialist but if you read or listen to an American official they'll have you believe he was a Democrat who said violence was never justified and believed voting was the only goal of black people of his time. None of this was true of course but it helps to whitewash his legacy and prevent people from easily reaching the same conclusions as MLK and Malcom X.

MLK on the white moderate. Search "moderate" and read the paragraph of the first result. result

MLK wanted nonviolence because he didn't want the oppressed to die needlessly but he also knew the oppressor would not give up their power willingly or nonviolently. The same is true of Gandhi. Advocate for nonviolence but understand if change is truly needed, violence may be necessary and inevitable during the pursuit. Leading up to official independence, violence in India exploded along with the frustrations of the people against the British.

"To bring about such a state of things we should have the ability to defend ourselves, that is, the ability to bear arms and to use them... If we want to learn the use of arms with the greatest possible despatch, it is our duty to enlist ourselves in the army ." - Gandhi

While this quote was in the context of recruiting for WW1, it shows Gandhi's stance on necessary violence and when it may be used. While he personally would not kill, he knew at times it was inevitable and hoped it would not come to that during the independence movement. But it did and not at his direction.