How did Moise Tshombe become prime minister after leading Katanga's secession?

After leading the secession of Katanga and subsequently being defeated by United Nations forces in 1963, Moise Tshombe went into exile in Spain.1

He returned to the Democratic Republic of the Congo in 1964 at the request of President Joseph Kasavubu. The central government was facing a severe crisis due to widespread rural insurgencies that had broken out following the dissolution of parliament and the inability of the previous premier, Cyrille Adoula, to maintain stability.123

Tshombe was recalled to serve as prime minister specifically to quell these rebellions in the eastern Congo. He successfully utilized European mercenaries to help the central government regain control over rebel-held territories, effectively positioning himself as a "providential leader" of the very government he had previously sought to break away from.123