Unless the Holy Father was speaking in English or German, I doubt he said "Easter." Most other languages have some cognate of "Passover."
Same thing, anyway. Matthias was chosen to replace Judas after what we English speakers call "Easter," the day of the Lord's Resurrection.
Not wishing to be contrarian, but the only thing Easter and Passover have in common is the date. Jews would not be celebrating Eater at the time of Jesus because Easter had not been invented. Easter does have pagan fertility orgins while Passover has God-inspired orgins.