Could be propaganda

Furthermore, Plutarch records in his Life of Marc Antony that, in the years leading up to the Battle of Actium in 33 BC, Mark Antony was rumored to have given Cleopatra all 200,000 scrolls in the Library of Pergamum. Plutarch himself notes that his source for this anecdote was sometimes unreliable and it is possible that the story may be nothing more than propaganda intended to show that Mark Antony was loyal to Cleopatra and Egypt rather than to Rome. Casson, however, argues that, even if the story was made up, it would not have been believable unless the Library still existed. Edward J. Watts argues that Mark Antony's gift may have been intended to replenish the Library's collection after the damage to it caused by Caesar's fire roughly a decade and a half prior.