Why are interviews harder than the job?

I think there's also another element that the author is missing and that is likability. I've never experienced this, but I've heard about people being put through grueling interview processes merely to weed them out because they were deemed "not a good culture fit".

I think at least half of all interviews are a popularity contest, and the other half are your qualifications.

I don't think "popularity contest" is accurate, but cultural fit is both a real - and important - component AND a risky opportunity to apply massive personal bias. Lots of variability here; I have a coworker who asked the exact questions to all candidates to avoid this, while I can't stop going off script. I know my risk is higher but I also find better candidates (while very likely passing on very good candidates for the wrong reasons).

Not a fan on hiring based on popularity, but I do wish companies spent more time on actual culture fit and whether or not the person they are hiring is a raging asshole. I've worked with my share of "brilliant jerks" and they're just awful to be around. Even if they are John Carmack level of coding, it's not worth it--they are a net negative because of things like poor attitude, lack of communication skill, arrogance, my-way-or-the-highway stance on everything... I wish that filtering these people out was 50% of my company's interviews!

And I can tell from experience that it's quite easy to get rid of "brilliant jerks" during the recruitement process.

The key is to make them stop the process, not you; so you won't have to deal with HR or management telling you that they are brilliant and you should not reject them just because "you" don't like their behavior.

Scaring jerks out is quite easy: just be excessively nice during the interview. Tell them how much time and energy everybody take caring for each other's well-being and feelings. Tell them that in the team you have lunch together every single day. And you do stuff together after works. And during the weekends.

They'll just run.

Sure, you're lying because you're working in a regular team where people are simply respectful professionnals, but they don't need to know that. You'll do everybody's a favour. The jerk included.