Earlier quoted context omitted.
I just wonder why. It seemed like pardoning Assange and Snowden could win him a huuuge bonus to popularity among people all over the world. Perhaps that was considered "too much" and could probably imply worse consequences so he hesitated to.
He was investigated for 2 years and is still accused to this day for Russian collusion. Pardoning either Snowden, who is in Russia right now, and Assange, who is accused of being a co-conspirator in the Russia collusion accusations, would be like throwing gasoline on that fire. I don't see how he could do it without alienating most of his establishment support, which he still needs after leaving office.
Simply put, Trump was threatened that if he pardons Assange, senate republicans (the establishment) would vote to convict.
I wish he had the courage to call their bluff, because them convicting Trump would fragment the GOP to an extent that is irreversible, IMO. Most people who aren't Trump supporters don't appreciate the extent to which Trump's base is not overlapping with the establishment GOP base.