The movie has an overarching theme of the importance of heroes, and the power that one selfless act has to inspire others.

After Rey force-heals the serpent, she says to BB-8 “I just transferred a bit of life from me to him. You would have done the same.” Then, when BB-8 finds D-0, he transfers him a bit of energy, allowing D-0 to power up and, later, to provide key information about Exegol. So Rey’s good deed inspires another good deed, which leads to an even greater good being done for the galaxy.

Also, just as Anakin sacrificed himself to save someone, all of his descendants ended up doing the same:

Luke sacrificed himself to save the Resistance
Leia sacrificed herself to save Ben
Ben sacrificed himself to save Rey
Threepio sacrificed his memories to save the galaxy.

That’s why I love Hal’s “For Skywalker” scene: It takes that idea even further.