That link does not explain why the number of infections and deaths is peaking right now.

The short answer is Delta. The longer answer is:

1) Delta is enormously more contagious and so will tear through the unvaccinated faster and will create more breakthrough infections simply due to greater chances of exposure,

2) Delta is also more virulent and is more likely to put young people (who are less likely to be vaccined) in the hospital,

3) Breakthrough infections are more likely with the elderly or at-risk populations due to poorer immune response, and Delta being more virulent means they're more likely to land in the hospital, and

4) Assuming some reduction in vaccine effectiveness over time, that'll impact high-risk populations first since they've been vaccinated the longest. And those folks have a much higher likelihood of ending up in the hospital because of their high risk status.