tl;dr: It could be that the fatality estimates aren't well made; supporting the 2022 FIFA World Cup in Qatar, however, supports well-documented abusive work conditions of foreign workers.
I've tried to dig up some sources on the numbers.
The 4000 deaths estimate was originally made in the ITUC Special Report [1] from 2013-2014, based on how many foreign workers from certain countries where numbers were available. This report mentions "These cases documented by our legal team, show the serious abuses of 1.4 million migrant workers in Qatar."
I don't know if they mean that only 1.4 million of 2.6 million migrant workers are abused, or if they assume different base numbers. I also don't know how they reach the number 4000, but on page 15 of the report you can see that they claim that this number is connected to the construction of the one dozen stadiums for the world cup, since they compare the number 4000 to numbers for similar sporting events in the past where fatalities range 0-40. (0 is London in 2012, 40 is Athens in 2004.)
The report does not spend a lot of time justifying the 4000 deaths estimate, but a Washington Post article from 2015 [3] mentions another report from 2015 by Engineers Against Poverty [2] (404s, fetched from archive.org) that reads:
> Overall, a report commissioned by the Qatari government shows 964 deaths of migrants from India, Nepal and Bangladesh in 2012 and 2013.
Subsequently, the number 4000 was controversial and was estimated both as high as 6500 in 2021 [4] (still only for certain countries where numbers were available), and as low as 3 if you ask FIFA.
Interestingly, BBC was thrown in jail for reporting on this. [5] Can't have all those fake news.
Maybe you're right and there isn't an unusual amount of deaths in Qatar. Maybe there is, and the numbers don't add up. Maybe they don't add up because they're super imprecise, and maybe they don't because they didn't account for statistical factors such as average deaths in construction work world-wide.
[1]: https://www.ituc-csi.org/IMG/pdf/the_case_against_qatar_en_w... [2]: https://web.archive.org/web/20151024015052/http://www.engine... [3]: https://www.washingtonpost.com/news/wonk/wp/2015/05/27/a-bod... [4]: https://www.theguardian.com/global-development/2021/feb/23/r... [5]: https://www.bbc.com/news/world-middle-east-32775563
Google tells me that the population of Qatar is 2.881 million. If 90% of that is foreign workers, that's 2.593 million foreign workers.
The timespan for those 4000 deaths in your link is not given. I'd guess it is over several years since the construction projects for the World Cup are taking place over several years, but let's put them all in one year just to make sure we aren't giving Qatar the benefit of the doubt. I'm also going to assume that most of the workers are young but not children.
4000 deaths among 2.593 million people in a year is a death rate of 154 per 100k per year.
For comparison, the death rates in the US [1] for males ages 15-24 is 100 per 100k per year, and for ages 25-34 it is 177 per 100k per year.
Without more to go on, it looks like the 4000 deaths might just be about the normal number of deaths one would expect in a group that large.
[1] https://www.statista.com/statistics/241572/death-rate-by-age...