Title in scare quotes are because, "Diminished Biden", "Functioned" and "In Charge" do not go together.

Criminal Biden cannot be, and is not, in charge.

But WSJ at least says what "we" saw all along:

Aides kept meetings short and controlled access, top advisers acted as go-betweens and public interactions became more scripted.

...staff repeated basic stage directions, pre-screened donor questions, and ended meetings when he had "bad days"—all while insisting publicly he was fit to serve