The end of February, 2019, we received a number of news reports that Mueller’s final report was soon to be released. This seems unlikely because there are quite a few more threads of this investigation that have not been explored.
Mueller just might release a first report followed later with further report(s). If this is what actually takes place, here are some possible reasons why:
The president was found to be an agent working for Russia and his alleged actions to diminish the United States need to be stopped.
The president is slowly turning this county into a dictatorship and this needs to be stopped.
The president is close to shutting down the Muller investigation and needs to be stopped.
Mueller is not confident that delaying the report will see the light of day when it is placed on the desk of the attorney general and placing a first report that shows the vast importance of the investigation would ensure that the investigation continues until all the threads are examined.