Is one program dependent on the other in some form?
To my knowledge, yes. The Artemis program is NASA's initiative to get humans outside of LEO again, starting with the Moon and onto Mars. Starship was started because of the NASA contract awarded to SpaceX to create a vehicle to ferry astronauts to/from the lunar surface from an orbital lunar space station. Without Artemis, there was no contract to spur along the development of Starship. And without Starship, there's no way to ferry astronauts from Orion to/from the lunar surface.
The irony is the deep desire for cost reduction at the outset of the development of the program has been the root of the cost overruns. The decision was made to reuse engineering designs which had their origins in the 70s (which eventually became the Space Shuttle) as the basis for the launch vehicle for Orion. All of that equipment had to be re-engineered for applications not originally intended, lines that had long been shut down reactivated, and for what... making 50 year old designs come alive again? Did we save money by taking a shortcut with "proven" designs, that had to be reverse-engineered by teams of people who had to do all the flight engineering work all over again? Certainly not!
I agree, there is a huge money pit under SLS. But like the similarly bloated F35 program, at what point is it too big to kill? Pull the plug after the bulk of the investment has already been made, with no opportunity to take advantage of the money already spent? Developing an alternative will be equally costly and egregiously time consuming. Finding an off-ramp may be the best solution, but I can't help but feel like it may be premature to put all our eggs in one basket when we still have no idea what will hatch from them. It's all the more impressive to look back at the Apollo program of the 60s with the more limited technology available to them at the time. To do what they did back then in the time they took, with what they had, is astounding.
Can you elaborate on what you mean by "Is SpaceX getting off easy because they're hiding in the wake of NASA's prudence?" ?
NASA is taking intense heat for cost and time overruns (perhaps rightly so). Because of the SLS time and cost overruns, it's giving SpaceX gobs of additioanl time to work out the issues with their own designs. Put another way, NASA nudges the launch date for Artemis II and III by a few years, giving SpaceX more time to figure out their end of the program while NASA takes the heat for another delay. If you recall in 2022 when Artemis I first rolled out, Artemis III was originally scheduled to launch sometime this year, and it would have required Starship (refueled in orbit) to have been ready by now as its crew's ferry to/from the moon. If Artemis I hadn't been delayed due to fuel leaks on the pad and Artemis II/III not delayed even more due to heat shield investigations, we'd quite possibly be on the moon figuring out more about how to make life on Mars possible by now. Or would we - with Starship still being 2-3 years away from the point where it can refuel in orbit and do its job as a lunar ferry? In this vein the point is that I think SpaceX is not in the crosshairs for their own delays because NASA's delays have been drawing the attention of everyone, buying them time.
Overall I think my point is that while
something needs to be done about the costs of SLS and Orion, pushing the proverbial "nuclear" button to kill it before it's done its job is both the most drastic option and, IMO, the most hasty. As they taught us at US Space Academy, "Undue haste makes waste".
The wheels of government turn slowly (or backwards, as my wife puts it), but when we've gotten this far - do we waste the product or use it for all it's worth?