If Trump was investigating Ukrainian corruption

Why was it not investigated through appropriate and OFFICIAL channels such as the State Department, the CIA etc.?

Instead the Dummy-in-Chief had Giuliani, his personal lawyer, do it. This is exactly what Nixon did with the Plumbers, which became his own personal investigatory group of buffoons like Howard Hunt and Gordon Giddy.

I hope our Ds make this analogy. If it was really an official investigation as to foreign corruption, there are plenty of lawful ways to do that. Rudy Giuliani is not one of those ways.