And under what section of the Constitution was Congress given the power to grant any jurisdiction in these matters to lower courts?
Article III.
As I pointed out above, President Washington and the very first U.S. congress decided in the Judiciary Act of 1789 that the Supreme Court's original jurisdiction would NOT be exclusive for certain types of cases, for example as to cases brought by ambassadors.
You may recall that a lot of those folks had something to do with writing the Constitution.
But it's good to know that you know better what the Constitution means than the people who actually wrote it!