You are right in the sense that eradicating poverty will probably have a stabilizing effect on many societies, but, in Brazil at least, it wasn't the poorest who supported the rise of fascism - this was driven mostly by the middle class.
In Germany it was the hate speech, the scapegoating, the xenophobia of the nazi discourse, the framing of other people as sub-human, evil and unworthy of living. This led to seemingly normal people inflicting unspeakable evil upon others. And it's frighteningly easy to make a human do that.
That's quite literally Nazi propaganda, although the narrative was born in the US with Keynes as Americans were oddly keen on washing the Germans of their sins, shifting the blame everywhere else and go back to business as usual.
The Treaty of Versailles was nothing particularly odious, Germany could have coped with it fine if it stuck to the terms. It didn't, it broke its economy on purpose to avoid honoring the treaty.