I find Volker's transcript to be the more interesting:
"Volker undercuts Sondland’s defense, says Giuliani pushed ‘debunked’ claims
While that may be Sondland’s defense, it’s clearly not Volker’s. Volker testified that it was clear as day what Giuliani was up to.
He also agreed that theories pushed by Trump and Giuliani had been “debunked” and weren’t credible:
Q: So is it your testimony that you understood that Rudy Giuliani’s desire for the Ukrainian government to investigate Burisma had to do with potential money laundering or other criminal conduct by the company itself, and not in connection to either Joe or Hunter Biden?
VOLKER: No. I believe that Giuliani was interested in Biden, Vice President Biden’s son Biden [sic], and I had pushed back on that, and I was maintaining that distinction.
Q: So you were maintaining that distinction, because you understood that that whole theory had been debunked and there was no evidence to support it, right?
A: Yes.
At another point, Volker says he urged Giuliani not to investigate the theories pushed by former Ukrainian prosecutor general Yuri Lutsenko because they were specious.
“I reached out to him to brief him, a couple of key points: Lutsenko is not credible. Don’t listen to what he is saying,” Volker said."
And:
"When Volker was the first witness to submit to a deposition, Republicans insisted that his actual testimony — rather than the select text messages Democrats released — was actually good for Trump.
There is, quite simply, little sign of that here. Volker does say that he didn’t have a quid pro quo communicated to him, but he doesn’t say there wasn’t one.
“Well, you asked what conversations did I have about that quid pro quo, et cetera,” Volker tells a member at one point. “None, because I didn’t know that there was a quid pro quo.”
He adds at several other points, under questioning from Republicans, that a quid pro quo had never been expressly communicated to him by either U.S. or Ukrainian officials.
Q: That message that I heard you very loud and clear today is that there was no quid pro quo at any time ever communicated to you. Is that correct?
VOLKER: Not to me, that is correct.
That’s significant because it suggests this perhaps wasn’t so overt. But Volker has an incentive to argue he didn’t explicitly participate in a quid pro quo that Sondland suggested might be illegal. And as Sondland’s testimony makes clear, it was pretty evident what the arrangement was.
Rep. Mark Meadows (R-N.C.) tweeted after their testimony was released, “The Volker/Sondland transcripts lay it out: @realDonaldTrump wanted to clean up corruption in Ukraine, and ensure taxpayer funded aid wasn’t going to corrupt causes."
The transcripts, in fact, show both Sondland and Volker believed Trump was interested only in investigations that carried personal benefits. Sondland even concedes how problematic the specific investigations were"
So...while everyone dances around the quid pro quo question..it is clear that most of Trump's advisors tried to warn him that his actions were based on debunked conspiracy theories....the same theories that some here give credence to.