What accounts for the movement of many African Americans from King's "beloved community" ideal to "black power" slogan popularized by Stokely Carmichael and H. Rap Brown? This is from chapter 19 of a textbook called The Struggle for Freedom.

The civil rights movement's slow pace frustrated many black people, who believed that desegregation was only the tip of the iceberg of problems that blacks needed to address. Martin Luther King's "beloved community" was a slogan intended to preach nonviolent resistance.
The Black Power movement was born in 1966, and it gained momentum under the charismatic leadership of Malcolm X. After Malcolm X's death, the Black Panther Party was established by Huey Newton and Bobby Seale in Oakland, CA. The group's original aim was specifically to end police brutality against blacks. This radical activist group (also promoted by Stokely Carmichael, who coined the "black power" rallying cry) was in many ways a reaction to the existing call for civil rights reform, which held that the speed of reforms ought to be sacrificed in the name of peaceful resistance. As a group, Black Power activists rejected integration and instead promoted separate, all-black institutions in the control of black people themselves. This group highlighted the injustices perpetrated by white people against black people for centuries, and it sought more reparations than simple desegregation; the proponents of black power wanted justice. This movement was especially popular with younger people, who grew impatient with the more peaceful strain of civil rights activism popularized by Martin Luther King.
Spike Lee's 2018 film, BlacKkKlansman (sic), is an excellent portrayal of the tumult that occurred in 1970s owing to racism, and it features a fictional portrayal of Stokely Carmichael.