Garland Nixon explains why.
Simplicius gives an in-depth analysis here
“I bet Raytheon is pissed that we sent the Patriot systems over to Ukraine.”
My first thought. One of the reasons that I opposed our involvement in this war was that the neglect of our military for the past 35 years would finally come to light (after all why have a fully modernized military when you only plan to fight Third World countries?), and therefore our threats around the world, where we actually do have legitimate interests, would be empty.
...and it all happened as I feared. We gave Ukraine HIMARS, and they did well with them, but 6 months later, the Russians have neutralized them (not too smart relying on GPS when fighting a peer-level country, but then it does work in my car, at least). The titanium M777 Howitzers were even worse, barely noticeable on the battlefield.
...and now the Patriot, our meager attempt at trying to match the S300 (not to mention S400, S500, and now S550 which can also take out satellites). The Soviets and then Russians took air defense seriously; we figured it wasn’t needed and we couldn’t find more than a few dollars in our trillion dollar military budgets for it (fighting useless wars in the Middle East and dozens of other places is expensive, by the way).