They are doing exactly that already, partnered with an established company with proven design to help them ramp up production by manufacturing some hard-to-come

They are doing exactly that already, partnered with an established company with proven design to help them ramp up production by manufacturing some hard-to-come-by parts. And then Musk decided to burn some money on top of that, trying to find a way to produce even more machines from existing parts and/or parts that he can get more easily. And people give him shit for that? Seriously? Has their effort to produce a ventilator like that a high chance of failure? Sure. But maybe their hail marry will succeed and save lives after all. And if they fail, at least they will have tried. The only actual problem here would be if they produced a worse-than-useless machine that kills people but is put into use anyway. This hasn't happened yet, tho, but people right now are attacking this strawman viciously anyway.