In my opinion, the notion of Luddendorff as a 'prodigy general' has far more to do with his linkage to v. Hindenburg, his role in the mythologizing of the Eastern Front in WWI (specifically at the Battle of Tannenberg), a limited period of efficacy on the Western Front, and his later effusive support for the false narrative of the Dolchstoßlegende (stab-in-the-back theory). In truth, Erich Luddendorff was more in the right place at the right time serving alongside Hindenburg, and managed for a time to leverage the Field Marshall's prestige and the precarious state of the German war effort to achieve significant power. I do, however, reject the notion that he had some sort of 'absolute power, as evidenced simply by the fact that he was removed from command by the Kaiser with the support of Hindenburg in 1918. While he attained an almost unprecedented level of control over the military and political decisions of Germany for several years, he was unable to leverage that control for any sort of long term political power or to achieve any of the major goals for Germany victory (overseeing instead, in this case, punishing defeat).

Quick note on sources, because so much of the way Ludendorff is characterized depends on who is writing about him, at what point in time, and to which audience. The largest bulk of the lionizing of Ludendorff came from his own (anti-semitic, nationalist, deeply bitter) writings as well as the later co-opting of his image for Nazi propaganda purposes (e.g. his highly publicized Nazi state funeral, performed against his express wishes to not be linked to the nationalism of Hitler and the NSDAP). My principal source is the writings of English historian John Wheeler-Bennet in his 1936 book Wooden Titan, a biography of Hindenburg that drew on the author's many personal interactions with key players in early 20th century Germany. I will acknowledge up-front that by his own admission Wheeler-Bennet found Luddendorff irritating on a personal level and thought he was grossly incompetent at understanding the political dynamics of command. That said, he also referred to Ludendorff as "certainly one of the greatest routine military organizers that the world has ever seen," so he wasn't completely biased against the man. I also think Wheeler-Bennet's work can serve as an excellent primary document of the way Ludendorff was perceived by his peers in the German military and political classes. Moreover, much of the characterization of Ludendorff as a relentlessly ambitious, inconsiderate, temperamental, and ultimately ineffective is backed up in references in Hans Mommsens' The Rise and Fall of the Weimar Republic and Karl Dietrich Bracher's The German Dictatorship: The Origins, Structures, and Effects of National Socialism. Both of those later works focus on the transition of Germany from Imperial to Democratic to Fascist rule, and in the process both authors pretty roundly condemn Ludendorff (and Hindenburg) as an overinflated figure tied up in nationalist fictions of conspiracy against Germany. Barbara Tuchman in The Guns of August basically describes the man as a devoted soldier but ultimately a friendless, egotistical asshole. My point is that Ludendorff was not by any means popular amongst his contemporaries - he was tolerated when he was doing good work and tossed aside when he was no longer seen as doing so.

So - what did Ludendorff actually do, and how can we assess it? We could definitely go down a major rabbit hole here, but I find the salient details can be very roughly reduced (in the name of brevity and simplicity) to four points:

1. Ludendorff's rise and fall were directly linked to his association with Paul v. Hindenburg. His initial successes in Belgium earned him some recognition, but they were not by any means central to his personal mythology until well after the war and in his own extensive writing. In fact, Ludendorff had the immense fortune to be assigned to Hindenburg as Chief of Staff and thus to be part of the war on the Eastern Front. While it is true that Ludendorff managed to supplant Hindenburg in many of the decisions made in the latter part of the war, Ludendorff was given power at the pleasure of Hindenburg, who had the almost full trust of the German Public as well as the Kaiser. In numerous instances (at Tannenberg, while in command at Kaunas, during the British victories at Cambrai and Vimy Ridge, etc.) Ludendorff was extremely emotional and tried to change battle plans in the moment, reacting to swings in the ebb and flow of battle. Both Wheeler-Bennet and Bracher describe Hindenburg, Falkenhayn, or other commanders as either calming or ignoring Ludendorff in order to maintain discipline. So while Ludendorff was a capable, perhaps even a remarkable, organizer of logistics, his ability to maintain battlefield calm was highly questionable, absent his tempering by the steadier hand of Hindenburg. Numerous sources report that Ludendorff twice tried to break off the assault at Tannenberg, fearing a Russian encirclement, but it was Hindenburg who held firm.

2. Ludendorff was in the right place at the right time. The victories at Tannenberg and the Masurian Lakes were massive, crushing defeats of the Russian army, true. This had every bit as much to do with the ineptitude of the Russian command, the lack of training and equipment of the Russian Army, and the German practice of destroying rails and supply lines to choke off their enemy as any battlefield wisdom. Moreover, while the victories in the East were undeniably significant, they were seen as truly heroic only in juxtaposition to the brutal, stagnant fighting of the Western Front. When one half of the military is seeing losses on a scale unprecedented in human history, the fact that the other side is scoring victories suggested some kind of innate genius on the part of Hindenburg and Ludendorff, when the truth was that the Western and Eastern fronts were entirely different sorts of conflicts, with the East being a far more advantageous field of battle for the German side. Ludendorff's later command of the Western Front coincided with collapsing support for the War in England and France and the withdrawal of Russian troops following the October Revolution. In other words, when he took over command in the West, it was against truly beleaguered soldiers and on fewer fronts than his predecessors. When reinforcements came from fresh American forces (joining the war after the unrestricted submarine warfare and international conspiracies like the Zimmerman affair that Ludendorff pushed for), his forces were unable to consistently hold off their foes and ultimately crumbled.

3. Ludendorff was a self-promoter of unrelenting ambition. He quickly recognized that he could achieve more under the much older Hindenburg by simply making command decisions on his own and by inserting himself into high-level deliberations. When he managed to irritate other powerful figures (such as Falkenhayn or Chancellors Bethmann-Hollweg and Michaelis), Ludendorff leveraged his connection to Hindenburg and offered their joint resignation in protest, knowing that the Kaiser would never sack someone as popular as Hindenburg. Ludendorff also inserted himself into the propaganda and industrial spheres of the war effort, seeking always to be in a decision-making position and portrayed in a positive light. Ultimately, Ludendorff's incessant efforts to get credit for the war effort resulted in his taking the lion's share of the blame when things started to go truly badly for Germany at the end of the war. With the Kaiser pushing for his removal, he again tried the joint resignation trick with Hindenburg, assuming he had the old man's total confidence. Instead, Hindenburg threw Ludendorff under the bus, and the Kaiser accepted only his letter of resignation.

4. Ludendorff was the sorest of sore losers. After losing his command, he acquired false papers and fled to Sweden, fearing that the nascent socialist revolutionaries in his country would blame him for the devastation of the war and hold him accountable for it. After the conclusion of the war (where Germany was left economically crippled, in civil turmoil, and trying to restructure their society in the absence of Imperial rule), Ludendorff launched an extensive campaign trying to blame the entirety of German defeat on sedition on the homefront, notably by internationalist (read: Jewish) banks and other elites (Freemasons, Catholics, etc.). His particular strain of virulent, anti-semitic nationalism was ineffective when he ran for office in 1920, but his participation in the Kapp Putsch in that year, as well as his role in the 1923 Beer Hall Putsch, were efforts for him to regain power by linking himself to the nascent Nationalist movements in Germany that resulted in the consolidation of power by the NSDAP. Ludendorff was again perfectly happy to link himself to others to achieve power, and he was again tossed aside when he was no longer useful. His early support for the NSDAP translated to his early lionization by the Nazis as a sort of a glorious martyr for the German nation, valiantly fighting in the Great War yet doomed by the machinations of the Jews, Catholics, and other traitors of the home front.