Basically there are three reasons why thorium power did not pan out when I was a kid:
1. The thorium cycle did not lead to or include nuclear weapons.
2. Admiral Rickover wanted power for his submarines in the most expeditious form, which was uranium light water reactors.
3. It was believed that uranium was very scarce and could not be diverted to start thorium molten salt reactors and had to be bred into plutonium for ever more bombs.
Number three turned out to be not true. Number two was a poor reactor choice for civilian use (sub-servient to the military, pun intended), and America’s greatest generation chose to make bombs for short-term military gain, instead of developing boundless energy for humanity that would be needed by everyone on the planet including us for all time.
Let’s be smarter this time.