(Update: as noted in the comments below, I've probably misunderstood the main point of the question. The answer below discusses the progressiveness of the taxation system without taking into account 'bracket creep', though the fact that most government expenses were paid for by printing money does partly answer the question.)

At the /beginning/ of the inflation crisis, the Weimar Republic did indeed adopt a more progressive tax regime. However, it was not enough to meet postwar expenses, especially given the fall in German production.

During WWI, the central government in Germany did not impose any income tax and financed the war almost completely via debt. (It had done the same during the Franco-Prussian, but that war was far cheaper and victorious.)

The Erzberger Finance Reforms of 1919 and 1920 transferred taxing authority to the Reich and raised the highest level of income tax from 4% to 60%. A steep inheritance tax was also introduced, taxing souses and children for the first time.

However to meet the postwar expenses, the government would have had to levy an /average/ income tax of around 25%, very high for the time and politically unviable. With no option to default and no access to the credit market, the government financed its deficit by printing money (or strictly speaking by issuing short-term notes that were bought by the Reichsbank for credit). This obviously accelerated inflation, essentially creating a flat (ie non-progressive) 'inflation tax' on money.