I think what Sondland has done has exploded the obstructive silence (in mafia terms the omerta) defence that Trump has employed. Until now, he had been trying the angle that the ambassadors were low level operatives who couldn't see the big picture. And the senior people wouldn't talk.
Sondland has revealed the conversation of the senior people: he has said Trump was in charge of a shakedown that all the senior people in the administration knew about and approved of.
So now those senior people are realising that to protect themselves, they need to talk.
This is, I think, the way they do mafia cases. Work their way through the people at the bottom towards the ones at the top. In the end, you get a circular firing squad, with all the main players shooting at one another like in a Quentin Tarentino movie.
Tonight, Pence, Bolton, Mulvaney, Pompeo, Giuliani are all going to be thinking about testifying to save their skins. Trump's conspiracy is about to fall apart. In the end, all the pistols will point in his direction.