I know of two examples from the Depression. In Germany, it was a deliberate policy. In France, it was a zealous adherence to the gold standard.

I am also bewildered. So many bad effects of deflation.

Politicians don't give a damn about deflation. They will tell you how governments must be responsible with their budgets and do debt ceilings and austerity, while simultaneously promising income tax cuts for the rich which they finance by cutting public investment. It'll trickle down.

Political constraints around central bank policy.

Or really strong deflationary market expectations, for whatever reason.

The problem is that you can get both at the same time: deflation of asset prices and inflation of goods prices.

Not if you need to import anything, since you can inflate your currency all you want, but the world will deflate it relative to other currencies.