1- The investigation did not stop, or slow down. Hence, as a practical matter nothing has been obstructed.

Attempted murder is a crime. Attempted Obstruction of Justice is not a crime. For Obstruction of Justice to be a crime you have to actually Obstruct Justice.

2- It's kinda hard for a sitting President with the power of Pardon to Obstruct Justice when that same President as the power to effectively dismiss the case by granting a Pardon.

The one exception to this would be if the FBI was investigating The President, because i don't believe a President has to power to Pardon himself.