Exactly! It's a shock absorber against cheating. Here's an example:
Let's say that in one state, the liberals manufacture 100,000 votes. If the popular vote chooses the President, then that would be added to the national total, and could well sway the election. However, under the current system, the 100,000 votes would be added to the state total. So, 1) at best, the fraud might have no impact on the election; and 2) at worst, it would only sway the state's electoral votes. Beyond that, it would have no impact. OTOH, every manufactured vote goes toward the popular vote total, and using that to determine the President would be a disaster.
So, it's a lot harder to rig the election under the current electoral system. It would be even harder to rig the results using an electoral model in which each Congressional district decided its own elector, but with all the gerrymandering out there, it might not be the best idea.
Actually, to clarify what I wrote, fraudulent votes do get added to the national total as well, but they don’t really “count” in choosing the President.