What’s going on with covid death rates by age?

I assume/hope there’s a non-scary answer to this question, but I don’t have time to figure it out, so I’ll just throw it out here . . .

From the NYT today:

How can cases and deaths have declined by the same amount since January, given that older and more vulnerable people have been disproportionately vaccinated? Has the infection fatality rate risen among the young? Is this just an artifact of timing, lags, and maybe the choice of start date? Or . . . ?