By declaring, and establishing his 2024 re-election infrastructure, he could pre-emptively lock up the Dem political talent-for-hire.
This would deny access to them by other potential 2024 Dem contenders.
Also, it provides him a position of power and influence because other Dems would have to go through him to access the Dem talent-for-hire he controls.
It's a defense from the potential slings and arrows that will come from Hillary Clinton's direction.
Hillary desperately wants to become the first woman President ... at any, and all, costs to the Dem party and the country.
We live in a Golden Age of Sociopathic Narcissistic Megalomaniacs - Joe Biden, Nancy Pelosi, Donald Trump, Hillary Clinton, Vladimir Putin, Xi Jinping, Kim Jong-un, and Mohammed bin Salman.