Why did Goldstone flip-flop contra actual evidence?

NYT columnist Roger Cohen wants to know, as do I.

And a flip-flop it is, that South Africa's Richard Goldstone did, distancing himself from the report of his own UN commission on whether Israel, as well as Hamas, committed war crimes in 2008.

I have to quote extensively from Cohen's column to set the background:

He says his report would have been different “if I had known then what I know now.” The core difference the judge identifies is that he’s now convinced Gaza “civilians were not intentionally targeted as a matter of policy.”

His shift is attributed to the findings of a follow-up report by a U.N. committee of independent experts chaired by Mary McGowan Davis, a former New York judge, and what is “recognized” therein about Israeli military investigations. Well, Goldstone and I have not been reading the same report.

McGowan Davis is in fact deeply critical of those Israeli investigations — their tardiness, leniency, lack of transparency and flawed structure. Her report — stymied by lack of access to Israel, Gaza or the West Bank — contains no new information I can see that might buttress a change of heart.

On the core issue of intentionality, it declares: “There is no indication that Israel has opened investigations into the actions of those who designed, planned, ordered and oversaw Operation Cast Lead.”

It says Israel has not adequately answered the Goldstone Report’s allegations about the “design and implementation of the Gaza operations” or its “objectives and targets.” Victims on both sides, McGowan Davis argues, can expect “no genuine accountability and no justice.”

In short there is a mystery here. Goldstone has moved but the evidence has not, really.

Was it all the varieties of the "self-hating Jew" epithet hurled at him after the report's release, as Cohen wondered? Did Israel threaten not to let him in the country as a private citizen, which may have mattered indeed to an observant Jew like him?

We don't know because he's not talking, which makes it worse.

That said, it's arguable Zionism has won again.

It's won not because Goldstone is or was a self-hating Jew, but because he's no longer a self-examining one, or however we phrase it.

It's won because many low-key Zionists will see this as affirmation of their low-key intransigence, NOT toward Hamas, but toward the Palestinian Authority and the UN.

It's won because these low-key Zionists and semi-Zionists in the U.S., along with their Christian millennialist Amen Corner, will up the political pressure on Democrats and Republicans alike, when Goldstone's report offered at least the possibility of relief.