Trump probably wants to use military force to stop NK from acquiring thermonuclear ICBMs and transferring them to regimes like Syria & Iran and/or using against the US and its allies.  
It is very farfetched to assume that he is so callous that he would start a terrible war just to avoid possible problems from Mueller, who already has his own problems regarding his bromance with Comey, his gag order on a FBI whistleblower, his failure to investigate the illegal unmaskings, and his reliance upon a pathetic, false documents (i.e. the dossier) which the FBI relied upon and perhaps paid for along with the Clinton campaign and the DNC.

Do you think that it was a good idea to sell large amounts of US uranium to Russia?

Do you believe that the Clintons' Canadian "charity" did not receive $135 million as a result of the sale?

Do you think that Bill did not receive a $500K "speaking fee" from a Russian bank involved around the time of the sale?

If you answered 'yes,' then you are uniformed.