In the Expanded Universe, was there ever an explanation for why none of Anakin's friends saved Zmi Skywalker?
Lets say the Republic and the Jedi have no legal jurisdiction over Tatooine and are not allowed to swoop in and mass liberate all the slaves on Tatooine.
Okay, now lets say no one on Tatooine accepts Republic credits. Notice that after Wato rejected Qui Gon's offer Qui Gon took Wato's word that A) no one takes Republican credits and B) no one else has the starship parts he needs without checking. A planet run by the mafia and no one is a money changer?
Okay, even then Padme should have easily been able to buy Zmi Skywalker's freedom out of her own money. If they won't take Republic credits, buy a bunch of water, gold, starship parts or other trade goods that people on Tatooine wants and send some minions to Tatooine to buy Zmi's freedom and take her safely to Naboo or Coruscant. Easy peasy, lemon squeezy.
Tatooine only has about a hundred thousand people on it. While Padme probably cannot afford to free all the slaves herself, the planetary treasury of Naboo probably can. Since she is so beloved by her people, she could even sponsor a charity drive to not have to use tax money.
The Star Wars prequels had a bunch of boring Senate scenes that probably didn't need to be there. It might have made the Senate scenes slightly less boring and more plot relevant if there was an attempt to free the slaves on Tatooine that got bogged down in red tape. Perhaps disgust at this inefficiency and corruption creates a groundswell of support for the Sepratists.
George Lucas wanted Zmi Skywalker's death to push Anakin Skywalker to the Dark Side...
Well there is no reason that she had to die on Tatooine. A big problem with Star Wars episode 2 is that there were no real stakes as a completely expendable droid army fights a completely expendable clone army.
Lets say Darth Sidius/Palpatine manipulates events so that the Sepratists happen to attack whatever safe haven Zmi Skywalker is chilling at while Anakin is away at Jedi boarding school. Hah, now Anakin can be pushed towards the Dark Side
and be pushed into being extra brutal against the Sepratists which undermines the Jedi Council's trust in Anakin.
Here is another video distinguishing TNG from STD