They "shut it down" when it became public due to the backlash[0]. But not really, they just started working in secret. Now we have a secret ministry of truth[1] like some nations have secret police.
Yes, the disinformation board was actually an attempt to formalize and create some oversight over the ad hoc, unaccountable process that the government has to go through today to pressure media companies to manipulate and censor the public.
I prefer it this way. It's better for people to feel like criminals who whiteboard in backrooms how to manipulate public opinion by laundering prior restraint through putting pressure on the incomes of billionaires. Formalization of this process would just be permanent institutionalization, and the US government has shown throughout the 20c to now that a public board won't prevent abuses, abuses will just be routed around the board.
[0]https://en.m.wikipedia.org/wiki/Disinformation_Governance_Bo...
[1]https://libertyjusticecenter.org/media/social-media-censorsh...