At that time the Church was embrolied in the Arian heresy which basically claimed that Christ was a created being and not equal to the Father. Athanasius was a fierce opponent of Arianism and in got him into trouble with numerous Bishops who were Arians, which led to Athanasius being exiled on several occasions. The Church in trying to placate the Arians had played around with the idea of changing the Nicene Creed slightly so it would not conflict with the Arian philosophy. With Arians comprising up to 75% of the Bishops and Clergy at that time it was a distinct possibility that could have happened.
Despite being tried on trumped up charges in ecclisiastical courts and being exiled, Athanasius never wavered in his fight for the orthodox view of the Trinity espoused at the Council of Nicea. He correctly saw that by giving ground on this essential issue the Church would be making a grave error.
In other words he went against the popular opinion of the laity of his day, against the majority of the Churchs Bishops and Clergy and the Roman Emperors, several of whom were Arians. He fought relentlessly against the forces that wanted to change the direction of Christianity into the Arian model and mindset.
He fought for the orthodox ,traditional faith as it was at that time, which is probably why he is admired by many traditionalists today who see parallels in what has happened to the Church in the past fifty years or so and the situation that existed in his lifetime.
Deviation from the true faith and traditional Catholicism in the interest of placating those who don’t adhere to the same beliefs.