Anyone competent is loyal to the constitution, not any one president or government. To get to be a general you’re going to be in the military though at least four admins, so loyalty to even a single party is stupid. So if these trials are followed through with, everyone competent will be out.
Additionally this jumpstarts the yesman downward spiral of competency; if you bring bad news contrary to what the fascist leadership want to hear, you’re eliminated, leaving people that will only lie to the admin, leading to the admin to have false information, leading to bad orders, leading to people having to lie about the failure of those orders, and so on. Usually this can take a decade or more to cause a failure, but if you start the cycle with a highly visible purge, even if you don’t kill those purged, that cycle starts near the end of the cycle.
Tldr creating loyalists that have to bend reality to stay employed will lead to a spiraling effect of decisions and failures based on nonreality that will eliminate those creating loyalists.
That was a great summary of the effect this could have.
Hitler’s generals speedrun challenge
TBH, a lot of supposed Hitler incompetency was his generals blaming their own fuckups on him.