Anastasius was only the second pope to not be considered a saint, the first being Liberius. This is probably due to the problems Anastasius had in trying to end the Acacian schism.
If you recall, it all started some years back with the Council of Chalderon, which condemned the teachings of Eutyches and Nestorius, approved the twelve anathemas of Cyril of Alexandria and proclaimed the orthodox arguments on Christ's nature. This did nothing to heal the three way split which had developed regarding His Nature. There were the Miaphysites who saw the divine and human natures of Jesus to be united without mixture or confusion. They were against the monophysites who saw the nature as a single, inseperable one. The Chalcedonians saw the two natures as completely seperate and could not contenance either of the other two philosophies.
Fourteen years before Anastasius to the throne, Acacius, the Patriarch of Constantinople had written, and Emperor Zeno had issued, an attempt at peace-making, named "Henotikon". The idea was to acknowledge similarities and ignore differences. It accepted Chalcedon's condemnations and anathemas, but avoided addressing the nature of Christ issue. No one was satisfied and many were upset about the Byzantine emperor dictating doctrine which was the rightful position of the bishops. The Patriarch of Antioch was pressured into accepting the Henotikon. The Patriarch of Alexandria refused and was expelled. The Miaphysite Peter Mongos accepted the document and was given that patriarchy. Pope Felix III condemned it after two years of indecision, at which time he excommunicated Acacius. This Acacius died in 489. the emperor died two years later. The new emperor, Anastasius I, accepted the Henotikon, although it did not make much difference to the Chalcedonian members of Constantinople.
So, in 496, the first thing the new Pope Anastasius II did was to send two bishops to Constantinople to meet with the emperor. The pope sent a letter offering to accept the baptisms done by Acacius and then let the whole issue be decided by divine intervention, not civil authorities, but Acacius' name had to be removed from the official diptych. This was the official list of those with whom the Church was in communion. The emperor was willing to cooperate, but said he would accept the Henotikon. Meanwhile, one man, Archbishop Andrew of Thessalonica, a previous follower of Acacius who had repudiated the Patriarch, asked to be allowed back into the Church. Between the pope's letter of reconciliation and his welcoming back of Andrew, bishops, priests and laity of the West turned on the pope. Many refused to receive Communion from him. A large division occurred between the moderates who wished to see this schism relieved and those who were resistant to any moderation. Pope Anastasius was labeled a traitor.
At the height of all this, Anastasius II died suddenly. Enemies said it was divine retribution! The split between factions grew! The anti-conciliation group named Symmachus as the successor. The Senator Rufus Postumius, an ardent supporter of the dead pope, supported Laurentius, causing the faction in the West to grow and the faction in the East to be ignored.
To underscore how horrid future generations thought Pope Anastasius II, the Liber Pontificalis called him a traitor, joining those who claimed so immediately. The Decretum Gratiani claimed "Anastasius, reproved by God, was smitten by divine command." Dante put this pope in the sixth circle of Hell in his book, The Inferno, a place reserved for heretics.
Even with all that anger, Pope Anastasius II was buried in St. Peter's Bascilica.