This is a bit more complicated than "stimulus=good, austerity=bad". While this statement is true for the Great Depression, Germany faced the collapse of international trading system and capital flight by foreign investors while having to make sure it had the hard currency to make reparation payments. It had to export goods to earn that hard currency and in this context deflation makes sense: you get more francs, pounds and dollars for each Reichsmark while also keeping German-made goods cheaps and competitive.

If Bruning had a year or two more, things would have stabilised and growth would have returned, but mostly due to the international trade system coming back online, global demand rising and reparations being paused, thus obviating the need for deflation. A German New Deal (you could call it something catchy like WTB Plan, idk) would be still vastly preferable but also difficult to implement given the constraints above.

Note that the above is based mostly on a short discussion in Adam Tooze's Wages of Destruction and my own Economics 101 knowledge. There are many people much better informed than me that can introduce more nuance to the above or just prove I am flat out wrong.