In not so many words, Robert Mueller stated there is a great deal of work to be done using the information he provided in the Special Counsel's report. He did not come out of retirement to carry out a Special Counsel only because of a wayward president. Robert Mueller did this work so this level of corruption in a USA election would never occur again. That means Congress's requests for reports and supporting documents must be provided. There is legislation to be written and further assessment of a president that committed obstruction of justice.

Robert Mueller is a calm man and carries out work required to protect the USA. I am sure he expects Congress to take his work very seriously.