After the collapse of the Simba Rebellion and subsequent mercenary revolts, Belgium nearly lost its predominance in the Congo's mining industry.

So We can say that Simba rebellion was totally defeated by ANC and Tshombe.
No we cannot; you said that.

Notwithstanding this declaration, the rebels continued fighting in scattered areas over the next decade.

I thought Simbas were totally defeated in 1965.
The rebellion as a movement was defeated. elements of it survived and in fact are still present in the current Congo.