The data is clear - people are quitting in record numbers over the last 10 months. Also, the hiring numbers over the last several months have been record highs as well. This causes many problems for the organization - salary increases, knowledge loss, etc.
One area that managers should be paying attention to is onboarding new employees. If this isn't done well, you'll start a roller coaster of hiring/quitting that could have long-term damage on the organization.
Think of it another way, when you hire someone, they are deciding faster than ever if it was a good move. They have no qualms (nor should they) about leaving 4-5 weeks in if they don't like what they see. They can probably find another job quickly in this market. What doesn't make sense is waiting 2 years - who knows that the job market will be like then.
Which means the second that someone accepts the offer, you should start building the relationship and doing all the other things that great managers need to do. Make sure the onboarding is smooth and effective. Help the new employee feel part of the team and part of the company mission right away. Focus on helping them feel productive and important. They aren't the new person who has to work their way up. They are just as valuable as anyone else.
The managers who leave onboarding to HR or don't have a plan will suffer. Those will be the same managers who complain that people today don't have "work ethic" or "loyalty". Those are code words for "I still think I can manage like it is 1980".