So it turns out Witkoff isn't just a brainless crony who got the job for being Trump's golf buddy. Instead he's a Russian asset, and actively advising the Russian barbarians on how to best manipulate Trump.
Whilst negatively framed in the article, I don't necessarily think it's as bad as it seems.
Firstly, I think this is how negotiations have always been. Functionaries smooth the way before the ultimate power makes the final decision and signs on the dotted line. This will have always involved in some cases helping the "opposition" know the right things to say to their own government. Secondly, many of these negotiations will not have been by unified teams, there will always have been factions trying to see their version of the end deal takes priority over others nominally on their same 'side'.
Secondly, we need to consider what Witkoff's objective actually is - and that is serving his boss, Donald Trump. It's not Ukraine's best interest, or even the USA's national interest. Trump doesn't give a damn about Ukraine. He's "Master of the Deal", so he thinks he should have a deal on Ukraine and that's all he wants*. It doesn't matter what the deal is. In this context, he and his cronies see Ukraine as the weaker party that's easier to pressure into concessions. So if the USA can collaborate with the Russians to wring as much out of Ukraine as possible, as long as a treaty gets signed, their job is done.
[*] Of course, Trump also wants a Nobel Peace Prize, undoubtedly for no other reason than Obama has one and he hates the idea that a black guy who made fun of him has something so special that he as a billionaire white man doesn't. Trump will have to make do with FIFA's
hastily-conceived peace award.