Trump was likely advised that:
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The judge is likely to rule against him no matter what, and this case will have to go on to appeal.
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Anything Trump would have to say after the expert testimony basically blew the case out of the water, would just piss off the judge and make things worse.
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If there is any chance (thinking less than 1% here) of getting anything but a pre-determined guilty verdict from this judge, it would be immediately after the experts said there is no foul here (looks bad in public opinion). To have the judge basically rule the opposite of an expert witness, looks worse to have it happen right after the expert says the case should have never been brought. It should bolster the veracity of the appeal that will most likely become the next step.
So Trump - or likely his lawyer - is correct in having him skip another session on the stand.