What's obvious can be said stated about many situations. Yes, there are bad "DEI" hires, but there are also bad "Merit" hires as well. Just because someone is qualified doesn't mean they're the best person for the job. Qualified people can still make mistakes.
What's historically obvious is that "bias" is human nature and it occurs in the workplace. We hire who we like, feel comfortable with and also meets the minimum qualifications. Unfortunately, meeting the minimum qualifications was optional in the "not so distant" past, hence the need for job qualification postings and HR review of hiring decisions now. When you have the majority of hiring positions filled by one sex, of one race, bias has a tendency to occur. People hire who they feel comfortable with first, then they determine if they are also qualified (ie. this is how Trump selects his downline/Cabinet, or think "Good Ol boys"). This is how we historically ended up with only white men in board rooms in the past. One of DEI's purposes was to challenge this natural tendency of bias by pushing the hiring manager to look past their bias and build a team of qualified but different/diverse individuals.