I don't think OSS is particularly special though. If a state actor threw cash around they could find folks at many big companies to do their bidding. In my experience, commercial software reviews are susceptible to the same sorts of attacks as those listed in the article("please review my change ASAP because it needs to go into the next release before the deadline!").
I don't know what to do about this. You could subject approved submitters to better background checks. You can improve automated threat detection and code analysis. You can switch to safer-by-default languages that make backdoors and malicious behavior more obvious.
I wonder if the same issue exists in other engineering fields? Has anyone ever bribed an engineer to make a bridge or a water supply less robust?
Of course, this happens all the time, check the consequences of any earthquake in any corrupt country for the more visible examples