They could have kept Randle as he was a restricted free agent and they basically rescinded the restriction when they announced the Lebron signing. They did that because Randle asked to be let out because he knew they didn't have the minutes for all those guys. That is the real problem with that roster. Their just weren't enough forward minutes or touches for Lebron, Ingram, Randle, and Kuzma. They did have to rescind the rights to Lopez, though could have signed him after that using one of the exceptions they used to sign either Rondo or Stephenson.
But no, I don't think that team wins the title. Ingram can't stay healthy (which is why the Pelicans have been so bad with a pretty solid roster). Randle is ok, but he isn't Davis. Davis was a monster during the bubble. The Lakers needed that and frankly Rondo was great for them as well (the title team still had Kuzma, KCP, Caruso). Hart, Ball, and Lopez wouldn't have played better than Rondo, Green, McGee, etc. You need the All NBA caliber of players for that and I'm taking Davis over Ingram + Randle. If Ingram could stay healthy that might be different, but Ingram can't stay healthy and when he does play he just doesn't have the impact of Davis. Randle is fine, but that it all he is.
No title for the Lakers, however had they not traded for Davis, they would have had the 4th pick in the draft. It was sort of wasted on Hunter, but Garland went 5th. I don't think the Lakers would have won a title in 2020, but they might have this year if they had Garland, Lebron, Ingram, Randle, and Kuzma. Not great defense from that group, but a heck of a lot of firepower if they could have stayed healthy.
Also, the Lakers real issue was not acquiring Davis, but a cheap ownership group that let players leave for cash reasons (like Caruso) and the poor move going after Westbrook. They'd have been much better off just keeping KCP and Kuzma (and Harrell) than acquiring Westbrook.