Russia and Ukraine are actually having some level of ceasefire talks now, and that is a significant step towards peace compared to the status quo ante of Ukraine refusing to talk to Russia under any circumstances
Zelensky challenging Putin to fly to Turkey on short notice unscheduled and without the kind of setup and advance security one would expect of a state visit was already a longshot, and its more important that the delegations actually met and what they hashed out, or failed to hash out. And in this case, it basically amounted to Russia and Ukraine both sticking to maximalist positions and not really agreeing on either side to start seeking compromises or negotiate the granular details necessary to find peace- but they did agree to a massive 1000:1000 PoW exchange. Which is itself curious and doubtful since its unlikely the rate of PoWs taken has been remotely comparable, and the last year of body repatriations has been repeatedly 40:900 or so in each swap
I wouldn't really call a meeting which basically ends with "we agree to disagree" a great breakthrough or the beginning of ongoing ceasefire talks.
Even if Putin himself was too scared to drag his sorry ass out of the Kremlin, he could have sent his foreign minister Lawrow to Istanbul. Instead sending the minister of culture, an obscure guy who nobody had ever heard of, was unmistakably a gesture of disrespect, a figurative middle finger toward Trump and his efforts at brokering a peace deal.
Trump has next to no control over Putin, but he has control over Zelenskyy. Trump wanted to drag them both to the table, "now kith", but he can't control Putin.
Trump has no influence on Putin because he refuses to use any leverage the US could wield against Russia. His whole theory of the case is the mistaken belief that Russia being wronged by the West is the root cause of this conflict and that appeasing Russia would therefore lead to peace. The way the Istanbul meeting went down imho once and for all proved this assumption wrong.
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if Ukraine refuses terms that are acceptable to Russia, they'll continue to do battle and occupy more and more territory as they have the upper hand on the battlefield.
Essentially, the more Ukraine remains uppity making delusional peace demands, Russia will just continue to say no. And Trump will be more and more incensed with Ukraine until he pulls the plug. And if the plug is pulled, all of Ukraine falls.
You're essentially arguing that Ukraine must surrender unconditionally and simply accept every single Russian demand.