After transferring some $770 million in oil revenues to their own private bank accounts, dos Santos and his cronies became convinced that pluralism in their country would be a very dangerous thing for their future business deals. They also quickly abandoned their former Marxist beliefs in favor of the type of capitalist principles embraced by George W. Bush and Jacques Chirac.
In reality the "communists" in Angola were simply one Angolan tribal group, and the "pro-capitalist" UNITA were another, rival, Angolan tribal group. One group spouted Marxist rhetoric to please their Cuban paymasters, the other group spouted free market rhetoric to please their capitalist paymasters. That's about as deep as the issues of "left" vs. "right" went in Angola. The reality was tribal politics, not Marxism or capitalism.
And according to this acticle, the "communists" found no real problem switching to "capitalism" when it came time to switch from their former (communist) to their current (capitalist) backers. Once they did that, Savimbi and UNITA became irrelevent to their former backers, who simply switched from one proxy to the other.