They didn’t know for sure if they succeeded.
Chirrut and Baze died hoping that Bodhi managed to get in touch with rebel fleet.
Bodhi died hoping that rebel fleet managed to break the shield and that Cassian and Jyn managed to transmit the plans.
Cassian and Jyn died hoping that anybody listened to their transmission.
All they had is hope that their death wasn’t in vain. That they made a difference.
The rebellion is built on hope.