Because he’s a football coach and there is almost always an implication that you toe the line or face reprisal.

It’s also in poor taste. Jesus himself commented on performative piety:

“Whenever you pray, do not be like the hypocrites, who love to stand and pray in the synagogues and on street corners so that others may observe them doing so. Amen, I say to you, they have already received their reward. 6 But when you pray, go into your room, close the door, and pray to your Father in secret. And your Father who sees everything that is done in secret will reward you“

Very much not an accurate description of what was actually happening, despite what the court’s majority claimed (egregious and surely, at least often, willful factual errors in majority opinions are a hallmark of the Roberts court)

Luckily there are both witness accounts and photos in this case, so it’s pretty clear what was really going on.

> Why shouldnt the football coach be able to pray on the field, alone, without forcing their belief on others?

Because they're an authority figure in that context.

Same reason I can flirt with you, but your boss can't.

I strongly encourage you to glance at the dissents for that case. That is very much not the case. The Supreme Court willingly ignored very important evidence that was the case.

Because he's an employee being paid to do what he's told and the school told him not to because it was causing a disturbance. Why does he have to practice his religion on his employer's time? Let's say he was cussing during school hours, would it violate his 1st amendment rights if the school told him to stop?