The Fusion Triple Product, which is the key determinant of whether there is a self-sustaining reaction, increased faster than Moore's law up until about 2005. Then all the money went into ITER.
https://physicsworld.com/wp-content/uploads/2004/01/pwhoa4_0...
From the article at :
https://physicsworld.com/a/controlled-fusion-the-next-step/
more information about the triple product and the Lawson Criterion.