..."Go, descend - for your people that you brought up from Egypt has become corrupt." (Ex. 32:7)The many commentaries emphasize the fact that HaShem refers to the people as Moshe's people, specifically. Some explain that the ones who incited the madness were from the Erev Rav - the mixed multitude of non-Jews whom Moshe accepted into the camp during the Exodus of his own volition, without a directive from God. These rabble-rousers fomented the rebellion against God and ultimately led the rest of Israel astray to worship the Calf.
Others contend that the one personally responsible for the image of the Calf was Micha, who took a plate with the Ineffable Name of God etched on it along with the plate used by Moshe to raise the bones of Yosef from the riverbed of the Nile and cast it into the forge of molten gold, causing the Calf to rise up. Micha was one of the babies that the Egyptians took in lieu of finished bricks when the Jewish slaves failed to meet their quota. These babies were shoved into the unfinished holes in the wall as punishment for the Jews' underperformance. When Moshe confronted HaShem with a grievance concerning these babies, He replied that these babies would ultimately be completely evil if they were allowed to live and that this fate served them better. Moshe was allowed to challenge this, at his own risk; he rescued one child, and that child grew up to be Micha (Rashi, Sanhedrin 101b).
Either way, it seems like the "blame" for the sin of the Golden Calf can be traced back to actions that Moshe took. Not only that, but we know that Moshe committed a grievous sin by breaking the Tablets that were etched by the finger of God; who told him to drop them? And yet, not only do we see that Moshe is not punished, ultimately he is rewarded (when Moshe has to carve a new pair of Tablets, God makes a miracle that sapphire is found beneath Moshe's tent. He is instructed to make new Tablets, and whatever is left from the raw material he is allowed to keep, making him a very wealthy man)! What is happening?
The Seforim haKedoshim (the "holy books", a reference to those books that reveal the hidden elements of the Torah) put this parsha in wonderful perspective.
Moshe Rabbeinu was the ultimate leader, the "faithful shepherd" who was willing to risk all for his flock. At the first mention of the turmoil happening below, he immediately positioned himself "between" God and the Jews, advocating on their behalf and using all of his abilities to "placate" God's holy Wrath. He used logic, pathos, and even self-sacrifice by demanding that his name be expunged from the Torah in the event that God exacts punishment on His people.
But the ultimate act was when he descended from on high and broke the Tablets. When he did that, he placed himself among the "sinners" of Israel, showing HaShem that He would have to take retribution from him along with everyone else. He displayed his unyielding commitment to his people, unflinching in the face of Divine punishment, because that is what real leaders do. Through even the most trying of times, they lead their people and guide them, chastising them when needed, and defending them from anyone.
Moshe's willingness to protect his people even at their lowest state, because of their lowly state, reaffirmed his worthiness to be their leader, and HaShem rewarded him as such.