Wikipedia
Oakridge was a successful research reactor about 50 years ago. But it would require 20 years to commercialise as there are some specific technologies that need development to overcome the peculiarities of chemically processing liquid Thorium salts, none of which seem really blocking.
So given that, and the obvious safety and utility of a liquid fuel, and the abundance of Thorium, why did we not have commercial MSRs by 1975? Because MSRs don’t make Plutonium, which everyone needed for bombs. Now we have very significant “resources” of difficult to handle Plutonium as a by-product of Uranium reactors and 20 years developing Plutonium-Uranium MOX technology at Thorpe have not technically and commercially succeeded in converting it to re-usable supply of fuel. Annoying.
India is making a solid MOX fuel with Thorium for conventional solid fuel reactors which in theory isn’t a bad idea although with any MOX fuel, it alters the reactor behaviour which needs care to work out.