It seems this video is a few years old. I went online to find out what it was about and this is what I've found.
The team went to Italy in Nov 2019 . They were there to play a match against Lazio. Some of the fans and team members went to the Vatican to sight see or to attend Mass with the Pope.
THAT's what all this is about!. TBH I'm stunned that a whole lot of Scottish people went to visit the Vatican at all - whoever the Pope is at the moment! Mary Queen of Scots was a lovely woman who died faithful to Christ - put to death by her Protestant cousin Queen Elizabeth I, (Whom the Pope had excommunicated - and was no longer entitled to be called Queen due to an old agreement between King John and the Pope of that era) but on the whole, the Scots are notorious Calvinists or fervent adherents of the Church of Scotland. RC Aspirant to the Throne, Bonnie Prince Charlie had great success with them and they called for him to be their lawful King, but after his failed attempt to defeat the Hanoverian lot, the Scots more or less fell away from Rome and to this day - most of them have no time for Roman Catholicism at all. Though I believe that the odd one or two are faithful to the Catholic Church.

Here's a link to a news report documenting the team visit.
Celtic fans enjoying Rome despite warnings ahead of powder keg Lazio clash

Also, earlier that year, Scottish Celtic fans were part of an earlier disabled Pilgrimage to Rome in April 2019. Francis was given a Team Shirt.
So, THAT cheering for Francis possibly took place after most of them had toured the Vatican before the football match back in 2019

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