I have no idea why the Ukrainian government would rather have a war than agree to neutrality and the ukrainian people getting self-determination.

Because the U.S. has been using neo-Nazis and misleading promises and other pressure to force it into that position the whole fucking time (and probably e.g. Zelenskyy doesn't care and was allowed to be elected for exactly this reason anyway; we know from the Panama Papers he was taking fascist money...). Here's a good example.

National Interest - How the West Got Russia and Ukraine Wrong

For their part, the Ukrainians needed no instruction from the United States to embark on a policy of de-Russification. When Zelenskyy shut down Medvedchuk’s media companies in February 2021, it was viewed as a gift to the newly arrived Biden administration. After 2014, “you’re either with us or against us” became a pronounced feature of Ukrainian politics, and Washington’s encouragement in 2021 made it worse. Autonomy for the Donbas, the formula contained within the February 2015 Minsk-2 Ceasefire Agreement, was considered treasonous by powerful forces in Ukraine. For example, Zelensky was warned by nationalist militia leader Dmytro Yarosh after his election that such an offer would come at the price of his neck. Just a few days ago, the editor of the Kyiv Independent wrote in the New York Times that any concession to Russia over the status of eastern Ukraine would bring about the same fate for Zelenskyy that befell Victor Yanukovych, who was tossed from power in 2014. The United States supported all these steps, looking simultaneously toward bolstering Ukrainian nationalism and blasting the Russophiles.