At this point I’ll believe it when I see an independently confirmed measurement of a working prototype. This stuff seems to be perpetually 20 years out.
It is mental and political/financial.
Achieving ubiquitous nuclear power is more like achieving ubiquitous electric cars than achieving ubiquitous flying cars. It’ll probably happen any decade now, vs maybe never.
Not a prototype, just a breakthrough. 50 million C isn't something to cough at.