I'm an Australian year 12 Modern History student and am finding it really hard to wrap my head around the Weimar Republic. After the Kaiser abdicated and a republic was established, Ebert was appointed Chancellor. In my understanding that position would have been abolished with the monarchy, as the Chancellor acted as a Prime Minister would. If you have a Republic with a President, why did they keep the Chancellor?
The federal government was a cabinet government headed by the Chancellor and responsible to parliament. The president appointed the Chancellor and could authorise emergency powers.
It was still really a parliamentary, cabinet system rather than an American style presidential system. It was similar to the French Republic of the time.
Source:
Eric D. With, Weimar Germany: Promise and Tragedy (2013)