It’s not clear where Jesus is standing in the synagogue, or his relation to the man with the withered hand. One might imagine in a modern context that a physician would stand close to the patient, carefully inspecting the wounded area, but this is a modern expectation.
The synagogue was a meeting place for instruction and business. Groups of people tended to form around specific activities and lets presume that such locations are noisy. Jesus is specifically asking the man with the withered hand to make himself conspicuous, to stand forth and be seen.
Jesus could have followed the guy out of the synagogue and healed him out of view of the Pharisees, but instead he acknowledges the trap.