There would have obviously been a few ways that it could have not reached it's max but there woudl be a few ways that it wouldnt have started in the first place.

Firstly.
The main reason as lupin says is that his mind had been changed by fear. Fear does things to people and in this case it made fudge go 'Insane' if you take away the fear then the insanity would go away with it so if Voldemort never existed the Ministry wouldnt be under attack, Harry Potter wouldnt be in the ministry everytime something bad happens which would mean fudge would have less stress and less corruption.

Secondly.
If Dumbledore had taken the job as minister for magic in the first place then there wouldnt be any corruption as he is a good man.

Even though there was no chance that they could or would happen in the books are at 0% it would probably be the only way that it would have not reached as bad as it did but also Fudge was hanged by the ammount of power he had which shouldnt be given to one man.