This is a State Department affair; none of what you listed that he was busy doing has to do with the State Department. He could've literally told them "Hey, I want Cuba off the list", they could've given him a report to sign off on, and boom. Done. I hope you understand that while the POTUS has final say over their Cabinet, they have a Cabinet so that they can, like, delegate things to them. So that, like, they don't have to be laser-focused on one or two issues for their entire term. The US' sanctions on Cuba have unjustly crippled the nation for decades, but he waits 99.9% of his presidency to actually effect change on the issue, which, again, amounts to telling some people in the State Department to make a report and then signing off on it. What Biden's done here is fucking meaningless, and it's surely only so late in his term out of sheer cowardice that he thought it'd hurt his/Kamala's election chances in Florida. Fuck him.