July 20th plot was not a Resistance project – it was a full-fledged military coup (not just a plan, but an actual coup). Obviously, the conspirators were heroes – they risked their lives to achieve their objectives (and most lost their lives as the result).
And this time the conspirators were not traitors, but genuine patriots, because their ultimate objective was exactly what Germany needed at that time – negotiate acceptable terms for an immediate armistice (or at least ceasefire) on both Wester and Easter fronts (or at least on the former).
They believed that in order to achieve this very noble objective, they to assassinate The Führer, overthrow the Nazi government, establish the military junta and immediately start negotiations with the Allied powers.
Unfortunately for them (and for Germany), achieving these objectives was ‘mission impossible’. They could have assassinated Hitler, of course – it was pure luck that he survived the explosion (obviously, he attributed his luck to the support of the almighty Providence).
As for all other objectives, they had a chance of a snowball in Hell. Hitler had an official successor – Reichsmarschall Hermann Göring who would have immediately assumed the position of The Führer and (also immediately) suppressed the coup. Suppressed for a very simple reason – practically no one, military or civilian outside of a small circle of conspirators supported their objectives.
The conspirators made no attempt to isolate (let alone assassinate) him so nothing would have prevented him from becoming the almighty Führer. Not even the very creative Valkyrie operation.
And even if they miraculously managed to seize power in Germany, no Allied power would have even talked to them about anything but an immediate and unconditional surrender. Which was precisely what they did not want (they wanted the Reich to return its 1937 borders).
Consequently, July 20th conspirators were genuine patriots and heroes. Unfortunately, they were ignorant of the most basic facts about the Nazi Germany and the Allies, naïve and thus hopelessly incompetent. So it is no surprise at all that they failed – and failed miserably.