a) there were way more deaths in 2018 and 2019 than were expected, and
b) despite Covid-19, the excess mortality still hasn't caught up with 2018 levels
What am I missing here?
You can click the "weekly" button and you'll see that covid-19 is deadlier than earlier flus, but has been killing people for a shorter amount of time.
2020 is different because there is a clear step-change in death rate after week 11, and the implication/fact is that that is COVID-19.
The conclusion is that those deaths are excess deaths on top of those that we would have had as a consequence of the 2020 flu season.
How does that compare with 2018 excess death graph, clearly some other novel virus would have caused that, it broke all previous highs quickly.
In 2019 excess deaths increased at a roughly consistent rate of around 5,100/week to 56,806 excess deaths in week 11 and then stopped.
In 2020 excess deaths increased at a roughly consistent rate of around 2,500/week to 27,552 excess deaths in week 11 and then started increasing at a rate of around 15,600/week to 105,564 in week 16.
Again IANAE, but different flu strains have different mortality rates, but broadly similar behaviour in that they mostly go away after winter. The step change (caused by COVID-19) is the difference, and the new excess death rate is much higher than the 2018 rate.
Flu season every winter brings excess mortality. Also very hot summers, but there's less of a pattern.
> b) b) despite Covid-19, the excess mortality still hasn't caught up with 2018 levels
You are missing a big factor: COVID is not behind us, and this excess mortality is happening DESPITE a lockdown, which never happens for regular flu seasons.