He's got a book coming out and the censors control what will be in it. He gave a publisher a manuscript and the censors have whacked out the juicy stuff the publisher thinks will sell the book.
The censor is the brother of one of the anti-Trump rats. He tells the publisher that if the info he's slashed is already on the public record he can leave it in so the publisher should pressure Bolton to testify after they publisher preps him on what to bring up if he's asked or not to get those things, lies or not, on the public record.
Bolton has absolutely no moral compass. If something furthers his agenda and makes him a buck at the same time, he doesn't give a damn who it harms or even kills.
So, the publisher tickles people like Romney and tells them it would help them to have a friendly publisher and to therefore advocate for Bolton testifying. Bolton slips a few things to his loyal leaking crew about what he has to say if called to testify, and the snowball starts rolling down the snow covered mountain.
Whether it gathers enough snow to become a huge snowball that causes an avalanche depends mostly on how well Senators know Bolton and his games.
As usual, follow the money.
JMHo
Yes, follow the money. Bolton leaked the book, not Vindman's brother or anyone else. It makes the most sense.
Bolton has a book coming out, one of the latest in a series of "trash Trump" books. He wants to gin up sales so he announces he'll testify at the impeachment if subpoenaed. For a while it looks like he may have his chance but the pressure to allow witnesses has subsided. So he leaks the stuff from the book and suddenly the chance to appear before the television cameras has grown again. Bolton wants the face time on TV, he wants the publicity, he wants the visibility that will drive up the sale of his book. He's a media whore to begin with. He's the leaker.