Would you care to cite your specific source that the "data" be looked at a little more breadth?
As posts detailing the ineptitude and gross malfeasance of the MIH / CDC / FDA are being read on this site, and posts contending all the large "official"data sites are wrong in some way, sources for assertions are always instructive.
As of 29 January 2022, according to worldometers' "official" data,
( 5,669,541 global Covid deaths "officially" / 7,923,543,454 global population ) x 100 = 0.072 %
Less than one tenth of one percent "officially" Covid dead over two years worldwide, says worldometers' data.
So as one possible answer to your question -- "What do you think caused 2020 to spike by 500K?" -- bad data collection methodology and reporting might easily account as a good possiblity.
Death counts come from the CDC:
https://www.cdc.gov/nchs/nvss/deaths.htm
But the federal government is controlled by bad apples, so instead let’s look at Oklahoma.
For this site you can get how many people died each year in OK:
https://www.health.state.ok.us/stats/Vital_Statistics/Death/Final/Statistics10.shtml
* 2015 - 39,413
* 2016 - 39,277
* 2017 - 40,451
* 2018 - 40,930
* 2019 - 40,931
* 2020 - 47,734
Very consistent, until we hit 2020 where all of a sudden 6800 more people died than any previous year.
What specific mechanism caused those excess deaths in OK?
The data picture is very frustrating and exhausting. Questions are automatically met with stonewalling and ridicule. We’re slowly but surely creeping towards the “hang them from lampposts” method of discerning veracity...