The danish SAS pilots are unhappy with their emloyer right now,and show it to the world by turning up at this Ryanair thing. Ryanair can say "pilots from this great major is lining up to join, that's how great it is to work for us". Mutual benefit even if it's not "for real".
Few or none will have the guts to leave SAS (these are very union-oriented people), and certanly not for an outfit like Ryanair.