Excess deaths is difficult to estimate.
Epidemiologists use excess deaths as a general guidance towards the magnitude and direction of extra deaths, not necessarily need exact precise numbers. This is still extremely valuable since official reporting tends to underestimate true mortality rate, so it's an extra metric to triangulate the magnitude or direction of extra deaths, not the exact number.
First, the lock down disrupted the economy, which caused poverty, which causes deaths.
Partially correct, there is mental-health issues such as overdosing or suicides to take into account, but autopsies do give you numbers for those deaths so you can adjust. Deaths caused by poverty is more tricky, however most Americans were on unemployment assistance and US economy shrunk only -3.5% GDP, which is large, but not enough for mass-deaths. See US economy shrinking -30% GDP in 1930 Great Depression, far fewer deaths than you think from that era due to safety net programs.
Furthermore, due to population increase, a lot of of the estimated excess deaths is actually increase in natural deaths due to population increase.
Good thing excessive mortality calculations takes into account the average baseline death rate over 3 year period (2016-2019) which will account for multi-year increase in natural deaths and population increase since you are not do a cross-sectional sampling of a single year (2019), but multi-year average of baseline death rates to account for population rate changes.
