It was not an "irregular channel", it was a dysfunctional regular channel.

[kentuck]

It was made dysfunctional by Donald Trump and Rudy Giuliani. The right hand did not know what the left hand was doing. It was an impossible environment for a functioning foreign policy.

Unfortunately, the "regular channel" consisted of everyone in the top echelons of the State Department. They were working for both Donald Trump and Rudy Giuliani.

Just as Sondland said, "everyone was in the loop".

The State Department was weakened to the point where it was no longer capable of functioning.

[genxlib]

1. It was irregular in two ways.

1. Guiliani had no business being involved

2. Ukraine isn't in the EU so the Ambassador to the EU (Sondland) should not have been involved either.

They were both involved because they were not diplomats or experienced in the foreign service. And they were pliable to the executive wishes.