I assume that you are referring to the Mueller investigation which found at least 10 instances where Trump attempted to obstruct the investigation?
The fact that the investigation ultimately continued and achieved it's stated goal, investigation into Russian interference in the last Presidential election, has nothing to do with the charges that would have been laid against Trump if he were not President. Attempting to commit a crime is still a crime, if you attempt to kill someone and fail you are still guilty of attempted murder. If you attempt to rob a bank but the robbery is stopped either by individuals or security features you are still guilty of attempted robbery. Failing to achieve a criminal goal does not make you innocent of a crime, it just means that the crime you committed is generally slightly different than what you originally intended.
Just for all of the Trump worshippers who will be jumping in, and have jumped in, in attempt to protect their "chosen one" the Mueller investigation did achieve it's goal which was to determine whether there was interference in the last Presidential election by Russia or other foreign powers and if there was any connections between these powers and members of the Trump or other election organizations. Judging by the number of guilty pleas, plea deals, and successful charges laid it was certainly more successful than the carefully ignored Republican investigation into Hillary which spent two years to find nothing. The investigation was never about Trump except to determine whether there was any direct communication between him and Russia. The fact that he lied about business interests in Russia, while telling about his personal practices, were not at the time criminal since he carefully refused to answer anything under oath. The whole idea of collusion between Trump and Russia was promoted not by Mueller (who is a registered Republican) or the majority of the Democrats but by Trump himself in an attempt to discredit the investigation. The fact, something Trump has never been interested in nor, it seems, are his supporters, that the investigation was not dealing with collusion per say was something Trump carefully ignored and instead created a fiction where he knew he would not be found guilty.The facts are that if Trump were not President, and that the sitting Attorney General is on record as stating that a sitting President is protected from criminal actions, Trump would currently be resident at another federally owned and run building.