Nadler is postponing and evading Mueller and Barr interview in congress because of underlying materials exposing co-conspirators that are pulling his string. Republicans and the public are interested in the malfeasance that expose Nadler’s party lawmakers, journalists and bureaucrats who tried to frame GOP supporters for years using taxpayers money.
Mueller team could have concluded the investigation in 2017 knowing that there is ‘no there there’, but decided to extend the probe purposely to after the 2018 midterms in an attempt to entrap the president in an Obstruction hoax the same way as Steele and Nadler wanted to entrap the GOP in a Russian collusion hoax for political reasons. This can be understood from the malicious decision of Mueller and Weissmann to appoint DNC donors to investigate their political opponent and by stating that there is no evidence of no obstruction which is unprecedented and against the premise that everyone is assumed innocent by the law until proven guilty.