Your right. The President should use the lever of withholding aid to root out corruption. Especially if a former elected official is involved. It’s his job.
Biden was bragging on TV about doing just that.
I also don’t see anything wrong with what the President did. What’s more, if Hillary had won, and Trump had let it be known he would try again in 2020, and Hillary had immediately launched an investigation into Jared Kushner or Donald Trump Jr... no one anywhere on the Dem side would consider that an impeachable act. Hell, they’d cheer her on.