How would I structure an essay like "'Weimar democracy collapsed due to the failures of its politicians.' Assess the validity of this view."?

First, think of all the main factors that caused the collapse of Weimar democracy. It can often help to divide these into political, economic, and social factors - of course, there's overlap between these categories, but it can make it easier to remember and understand the factors to divide them up in this way, especially for a question as broad as this. In this case, we might identify the following factors:Political: failure of politicians (the question factor); weakness of Weimar democratic system; appeal of the NazisEconomic: impact of Wall St Crash; hyperinflationSocial: humiliation of Versailles (and 'stab-in-the-back' myth); conservative reaction against Weimar 'decadence'Now decide which factor you think is the most important. You might agree that the question factor (politicians' failure) is the most important, but in this case let's say you think that the impact of the Wall St Crash is more important. Then, as well as providing evidence to show why that factor is important (e.g. unemployment figures, businesses collapsing), you should also try and demonstrate why the other factors (including the question factor) are less important, and try to link them to your 'most important' factor. For example, you might say that the main appeal of the Nazis was that they promised to boost employment with public works schemes, and so if unemployment wasn't already high, people would be less concerned about that.