People wear some of the dumbest things to the Masjid. Some weird kid once wore a shirt that said “I like to do it all night long” on it and instead of being chastised by the uncles, they praised him for wearing a shirt that was referring to prayer and encouraged other youth to pray all night long as well.
Other shirts however, have huge essays written on the back. So huge that it takes a few Rakaats to read it all. And why are you reading it in the first place? Terrible.
The shirt was probably designed by the enemies of Islam to distract you from your prayer.