What happened to the Generals that Hitler fired?

In general (no pun intended), not much.

The German failure of Operation Typhoon in 1941 led to a process of cashiering generals for defeats or disobedience and this trend continued until 1945. The popular stereotype of the Nazi state is one ruled by terror and many German generals postwar would emphasize the danger they were in by speaking truth to power. But being "fired" by Hitler for the most part carried very little penalties.

Most of these officers retained their ranks and various privileges. Hermann Hoth's case was somewhat typical in that he was relieved from active duty in the aftermath of the loss of Kiev, but he was still a Heer officer and kept all his decorations. Others generals like Fedor von Bock and Heinz Guderian were relieved for their supposed failures in 1941/42, only to find themselves back on active service given the extremely dire straits of German arms. Gerd von Rundstedt was an exemplar of this revolving door of being relieved only to be pressed into further service; Hitler dismissed him in the aftermath of the Typhoon, then allowed von Rundstedt a face-saving leave, promoted him to command the West in 1942, relieved him again after the failure to crush the Normandy invasions, put him back into command of the West after the Allied liberation of France, and cashiered him for a final time in March 1945 when the Allies breached the Rhine River.

Von Rundstedt retained not only his rank through this seesaw of dismissals and reinstatements, but also his large dotations of money the state gave its successful generals. In a move that undercuts his reputation for strategic genius, Erich von Manstein used his dotation to buy a vast estate in East Prussia after Hitler dismissed him in the wake of the massive Soviet victories against Army Group Center in 1944. While there were some generals who faced a personal loss after dismissal, they were the exception. Erich Hoepner is an illustrative case. Hitler decreed this general was to be stripped of his pension and right to wear the uniform because Hoepner ordered a withdrawal of his forces before Moscow. But this was in direct contravention of existing military law and Hoepner was able to use the courts to reinstate these various privileges.

Hoepner was a participant in the 20 July Plot and put on a show trial and executed. This case was illustrative of where the dictatorship applied terror and extrajudicial punishments. Military defeat was one thing, but treason was another. Officers involved in the Soviet-sponsored Nationalkomitee Freies Deutschland (National Committee for a Free Germany/NKFD) or Bund Deutscher Offiziere (League of German Officer/BDO) were traitors in the eyes of the state. Not only were these officers punished in absentia, but their families were subject to Sippenhaft, a collective family punishment. As German military fortunes further waned, the line between treason and being defeated drew thinner. Yet, Hitler only really began to apply this harsher line towards officers in the last months of the war.

Even then, the application of punishments were erratic. As Robert Loeffel's research into Sippenhaft reveals, collective punishment for high-ranking officers' families tended to be more symbolic than real. Generals typically come from elite social strata and these families often retained access to elite social networks. Hoepner was able utilize the courts to redress his grievances and was even given the option of committing suicide instead of being subjected to a show trial. Harsh collective punishments tended to be reserved for lower ranks and those Wehrmacht soldiers who were not insiders, such as Volkdeutsche.

But more than a few German generals postwar were able to capitalize on the punishments meted out to the lower ranks to burnish their credentials as a type of opposition to Hitler. While they did not frame their actions as political or military opposition to Hitler, the collective approach of these men was to position themselves as professionals acting in opposition to a military dilettante. Yet, this type of "opposition" to Hitler carried very little in the way of either professional penalties or danger.