They say that most fascist governments fall apart because they actively despise competence, which it turns out you need if you are trying to run a country.
If the reality of a thing is in opposition to the regime’s wishes, you can’t just wish that away.
However, the regime will favor those who say “yes” over those who accept reality.
I once read an interesting book on the economy of Nazi Germany. There were a lot of smart CEOs and high ranking civil servants who perfectly predicted US industrial might.
It we loosen "fascist" to just mean any authoritarian government, there are many that run of very long time.
More importantly, maybe the Nazi's were competent at first, but they absolutely fell apart internally due to mistrust, back stabbing, and demanding of loyalty above all else. Hitler famously made many poor military decisions.
And as a government they'd still be in power 20 and 30 years later if they didn't start the war (judging from Franco's spain).