The general consensus among historians today is that the NSDAP was not responsible for the fire, but that they were preparing for some type of pretext to expand the emergency powers they already possessed. Several legal measures that greatly expanded the central government's power had already been instituted before the Reichstag Fire Decree. The emergency decree "For the Protection of the German People" of 4 February had granted the Chancellor the right to ban political parties, press organs, and lock up political opponents. Such decrees built on prior precedents in the 1930s when various central governments used the emergency powers of the constitution to curtail press freedoms and other political restrictions. One of the oft underappreciated Achilles' heels of the Weimar system was there was little in the way of judicial review for the constitutionality of the central government's actions. The Weimar constitution assumed that the central government would invoke these powers in good faith for the Republic. The actions of the Hitler Chancellery were decidedly not in good faith, even when measured by his less-than sincere conservative predecessors. The SA had already been elevated to the status of auxiliary police by 22 February and the groundwork was being laid for a quasi-legal attack on civil rights. The Reichstag Fire Decree provided a capstone for removing most of the civil rights protected by the constitution, yet many of these rights were in the process of already being stripped away.

Richard J. Evans at the LRB has a good book review essay explaining the mainstream historical opinion on the fire as well as the more heterodox historians who maintain the NSDAP was guilty of a conspiracy. In the end, whether or not it was a false flag will likely be unknown, but the answer to this particular question is irrelevant. The political winds were shifting towards a dictatorship already and the NSDAP was pressing all of its advantages towards that end.