I disagree that one particular group doesn't have a hold over the party. I think Bill Clinton proved 25 years ago that the centerists will crush anyone that gets in their way and they'll do what they want. Deregulation, NAFTA, welfare reforms, pushing a homophobic agenda to ban gay marriage, Clinton got everything he wanted.
Barack Obama again proved centrist dominance in the 2010s by extending the NSA program, passing the NDAA, killing the public option in Obamacare, and ensuring the misery of millions of Americans by bailing out Wall Street instead of homeowners, and ensuring the stimulus he passed was negligible in nature.
Joe Biden's victory over both Bernie Sanders and Elizabeth Warren, coupled with the air tight control that Kyrsten Sinema and Joe Manchin have on the Senate proves continued centrist dominance. Progressives lost control of the party in the 80s and 90s when all the FDR and New Deal Democrats were pushed out in favor of pro-corporate, Third Way Democrats.
Centrists have won almost every big, significant policy fight in D.C. over progressives over the past 30 years.