You're assuming the leaks are coming from Mueller's office.
I'm assuming they're not. In fact, I'm assuming that they're not even "leaks" because they're completely false.
This suggests to me that they're just made up out of thin air and are ultimately aimed at discrediting the media outlets that report on them. This suggests to me that they're coming from Trump allies in Washington.
Reminder: there are 15 zillion GOP conservatives who hate Trump. Trump demands companies bring jobs back to the US even if that is harmful to their bottom line. This is not a conservative position. This is not a GOP position. This is a Trump position.
Ivanka is 100% loyal to Trump. She will advise him to do what is in his best interests.
Loyalty vs ideology. Ideology is a dime a dozen. You can shake a Washington haystack and have 15 ideologues drop out at your feet. You’ll never find loyalty that way. It’s far more rare and far more valuable.
He should listen to Ivanka every single day and ignore most else.
If it turns out there isn't an obstruction investigation, you may be right about the sources for the article. It's not a crime to lie to the media. However, putting out a fake story that the President is under investigation, which leads him to send out a tweet seemingly confirming that, which gets blasted across the airwaves for a couple of days, doesn't really seem like a great strategy if you're just trying to prove the media falsely reported something, that likely won't be reported, and therefore only ever appreciated by core supporters who knew that already anyway.