You can absolutely delegate understanding. If you don't, you are screwed as a leader. In fact, one of the things you have to give up as a leader is being the smartest person in the room.
I'll even go so far as to say if you can't understand something through someone else's expertise, you will not get very far in life.
Er, no it doesn't. How much about each of Goldman's investments do you think David M. Solomon knows in depth? They make thousands of deals each year, it would be insane and unsustainable for him to have deep knowledge about each, so he delegates.
If you're talking about fundamental analysis, you'd also be wrong, as my copy of A Random Walk Down Wall Street makes pretty clear. "Know a bunch of stuff about a company" is not a good investment strategy, or at least does not keep pace with well diversified index funds.
I'll even go so far as to say if you can't understand something through someone else's expertise, you will not get very far in life.