Yesterday Trump fired Jeff Sessions and appointed a replacement. That replacement is now in charge of Mueller's investigation into Trump's manipulation of the 2016 election. That person can interfere with Mueller at will; Sessions had recused himself.
Trump is, essentially, trying to appoint his own prosecutor and investigators for the high crimes he is accused of. There will be protests across the US at 5PM local time. (The original post had a link to find your local protest.)
Mueller is not dumb and presumably planned for this eventuality. That might make what Trump is doing less effective than the president intends. It does not make it any less corrupt.