Now, what started as a response to his own personal pain has turned into a crusade for other kids, too. —"Florida Kid Helps Other Kids Say, 'Bullying No Way',"
Nick News with Linda Ellerbee

The first passage describes Jaylen's campaign as a crusade and a response to his own personal pain, while the second passage describes the campaign as a grassroots endeavor.

How would you describe the word choice of grassroots endeavor?

This word choice indicates that the second passage is meant for.