Well, the first phase in the Time Lords’ trial comes to an end as the Valeyard continues to press the issue on the Doctor’s guilt.
For whatever crime he’s supposedly committed.
OK, it becomes a bit clearer here. The Doctor is on trial for simply interfering at all. Just going to the mysterious planet (which turns out to be Earth but in the wrong part of space by a couple lightyears) is a problem, and are the Time Lords only getting around to charging the Doctor with that now? He’s been through at least six incarnations so far where he did a lot of interfering wherever he went. Why get after him in this incarnation? Is it because the Sixth is so darn arrogant even by Doctor standards?
Never mind. That’s what the Valeyard is trying to prove.
What crime did the Doctor commit on the mysterious planet? See it occurs to me that Glitz and Dibbler would have destroyed the black light generator without the Doctor’s help. All the Doctor does is prevent things from getting much, much worse.
See, the Immortal wants the Doctor to fix things, but he won’t let the Doctor turn the system off to do so because the Immortal believes robots are superior even if humans built them. Therefore, he matters more than the organic beings he is supposedly taking care of. And that means occasionally culling people, but the guard captain has been leading culling targets to the surface to live with the tribe. If the tribe stayed up there, great. Instead, those idiots thought the Immortal was dead and went down there to take his stuff, and all that resulted in was the death of Queen Katryca and one other combined with a culling order while the black light generator goes nuts.
Which would be where Glitz and Dibbler come into play as they convince the Immortal to come with them and bring all his tech secrets because they have a black light generator in their ship to keep the Immortal functioning. Sure, that doesn’t solve the exploding generator problem, but at least the big robot with the car bumper for a head isn’t there to stop the Doctor, Peri, and the guard captain from containing the explosion that could theoretically destroy if not the galaxy than at least the entire universe by flipping every switch possible and running like hell. All the human survivors get to the surface to live out the rest of their days, the Immortal is destroyed, the underground bunker contains the explosion, and Glitz and Dibbler get a chunk of the robot’s unbreakable metal to sell, so everybody’s more or less happy.
As such, didn’t the Doctor save the day?
Well, yes, but the argument is he shouldn’t have been there in the first place.
Time Lords suck with rules like that.