Dowd was either forced into resignation or Trump was "VERY happy" with him and he left on his own accord. Either way it doesn't look good. Here is the article Trump was crying about.
Clinton Impeachment Lawyer May Aid Trump in Mueller Response
"Mr. Dowd has been at the center of a string of embarrassing incidents, including one in which he wrote a tweet for Mr. Trump that raised new questions about whether the president had tried to obstruct the investigation into his former national security adviser, Michael T. Flynn.
One person close to the president who has urged him to dismiss Mr. Cobb and Mr. Dowd has been the Fox News personality Jeanine Pirro. Ms. Pirro, a personal friend of Mr. Trump’s and a former Westchester County district attorney, told Mr. Trump in an Oval Office visit months ago that Mr. Cobb and Mr. Dowd were leading him down a path toward his demise."