These sorts of challenges work great for engineering problems where a little bit of money and a lot of sweat is all that is required to figure something out.
Fusion research is not that- it needs very large equipment investments for decades for even the most trivial experiments.
If we had tried to get to the moon with the same model we'd still be waiting!
This is what is holding fusion from commercial viability.
Give me a modern tokamak with 75 years of known dynamics, increase the size and magnetic field (i.e. bring high temp superconducting wires to market).
At the very least you get something as a consolation prize that has real uses vs. decades of wacky research ideas that more than likely will go nowhere.
IMO thinking of fusion as needing a "silver bullet" to viability is one of the major issues. Everyone wants the sexy new reactor concept, but nobody wants to be improving the boring donut design that's on the edge of practicality.
$80 Billion was spent between 2014 and 2017 on R&D of autonomous vehicles [1]. That's 12 Billion / year (& numbers from a while back - I'm sure investment has kept going). The US government spends ~18 Billion on the entire DOE, the majority of which appears to be keeping facilities running / maintenance (even though it classifies all of that as R&D) [2]. Fusion saw about ~4.7 Billion in funding in 2022 [3].
Orders of magnitude matter and fission / fusion R&D has been criminally underfunded for decades.
Self driving is a little bit of money and a lot of sweat? Umm... I don't think I've ever seen such a major understatement.
The DARPA challenge kicked off a many many billions of dollars arms race of private capital and we're only just starting to see a trickle of self driving cars on the road some 18 years later. Not to mention meaningful R&D advancements in AI, sensing software algorithms, HW sensing capabilities, etc that have seen applications outside of self driving.
To be fair, a decent part of the current model for getting to the Moon does involve milestone based payments, with the general idea being that it's cheaper, more efficient and has fewer bad incentives than just endlessly funding until the desired outcome is achieved. IIRC pretty much everything in Artemis besides SLS+Orion is using a milestone based funding model (the lander, the space station, the various research orbiters and landers that started launching this year).
Fusion research is not that- it needs very large equipment investments for decades for even the most trivial experiments.
If we had tried to get to the moon with the same model we'd still be waiting!