The so-called (by the Dems) "Obstruction Episodes" included more participants than POTUS. Any of his staff or appointees and the like could have been indicted if there was any obstruction. Imagine if Mueller had found a true conspiracy. There would be a network of individuals involved, by definition of conspiracy, and indictments would build cases that would build toward indictment of the top of the conspiracy. Even if a case could be made and obstruction acted upon, there would be co-conspirators, co-indictments, and so forth. Once such cases were taken into the courtroom, the pressure on the President to step aside would mount. The grounds for impeachment would be well-formed.

In other words, the guidance that a sitting Pres could not be indicated, constitutionally, is a real issue but it would not stop indictments of other individuals who served at the pleasure of a sitting Pres. They might not even be employed directly by the Pres, if such a conspiracy to obstruct was a reality. So the constitutional issue would not directly apply.

What stopped Mueller from indicting others on this matter of obstruction? No obstruction, that's what.