It was actually confirmed in canon (or at least, very heavily implied) it was Palpatine who killed Padme. The TLDR is that even with the medical tech, Anakin was too far gone to be saved. So he used the force to siphon Padme's life force into Anakin. Why? Because Anakin betrayed the Republic, the Jedi Order, his best friend who was like a brother to him, everyone just to save his wife. And in the end, his vision ended up happening and she died anyway, except now Anakin had ruined the entire galaxy.

Therefore, this knowledge would further break Anakin and force him into being Darth Vader, Palpatines nice obediently little dog. And at least in the old EU, Palpatine even told him this at one point and dared Vader to strike him down in hatred. And when he instead bowed because he felt he wasnt strong enough, Palpatine was just like "That's what I though, bitch."

Because, you know, even if that wasnt entirely written down on paper yet in Ep. 6, it does make it that much more important when he finally does betray Emps to save Luke.