A lot of it has to do with how long it takes to find the right candidate. As someone who has been involved in a lot of hiring over the last 20 years, I can say there's been a huge shift within the last couple of years and open reqs get 10-25x the number of applicants, which instead of increasing choice in a positive way has just resulted in the average applicant quality decreasing. That means recruiters and hiring managers spend a LOT more time vetting and also invest in parallel candidates to try to hedge, because so many candidates applying are legitimately unqualified.

It may sound like I'm blaming candidates, and sometimes it might be fair to, but this is also a problem caused by companies not investing in training and hiring junior level employees, which means that people who are unqualified feel forced to apply for more senior roles, as those are the only roles hiring. It's honestly shocking how many candidates I've interviewed in my career who don't even meet the basic bar for the role they've applied for, and are essentially just hoping to get lucky and snag a high-paying tech job even if it ultimately results in them being terminated, they can collect a check for 3-9 months without delivering.

Mass applications, AI cheating, fraudulent representation (e.g. saying you are person X but are actually interviewing on behalf of person X who you are not), lying on resumes and in screeners, and even nation state attacks on hiring (see North Korea trying to farm tech jobs for money to get around sanctions), it's not great on the hiring side either.