The problem is that most investors are willing to invest in possible failures in areas where there have been successes–such as pharmaceuticals. “we know most drugs fail, but some make oodles of money, so…” New sources of energy are much rarer–the last one being fission (or maybe solar-electric) so it is harder for investors to see that they are risking money for something that has some failures but will suceed sooner or later. That is why most, although not all, fusion investors have technical backgrounds themselves so they can put fusion in context. (Also big money tends to move in herds and fusion is way outside the trodden paths of wind solar and geothermal where government subsidies can make a profit more likely, although far from certain.)
