The confidence has been build up since they know Giannis is in their side that's why almost all of the bucks players improve since they already trust each other's talents that's why we see some huge dominance on this last play even if no Giannis around.
That's exactly what happened to the Cavaliers, when they have Lebron, they were playing really well but when Lebron left, Cavaliers has become a shitty team, hope Giannis will stay with the Bucks for life.
And for sure once Giannis is on the court for sure all of the team will be crazy since the bucks is the powerhouse team for this year and they have huge possibilities to take the champ among the other team.
They'll have to pass the East competition first, last playoffs, they didn't win against the Raptors.