This is not a regular court proceeding, those rules do not apply. Even if they did, there are many exceptons to heresay rules in a standard court proceeding.
I think it is a shame that the hearings are not being rebroadcast on PBS or any other station.
We'll agree to disagree on any effects on the election. Neither of us knows, of course.
I will say, if Trump had not gotten caught and Biden was the nominee, or even just leading the pack before nomination, an announcement by Ukraine they were investigating him would have given Trump an unfair advantage.