Once you identify an emerging theme, how do you find the companies that actually benefit from it?

Let’s say you become convinced that something like data centers, nuclear energy, robotics, or AI infrastructure is going to be a major long-term investment theme. How do you go from the broad theme to the actual companies worth researching?
What do you do? Map the supply chain, look for companies providing pick and shovels, screen for companies with relevant revenue exposure, read earnings calls or analyst reports, look at smaller suppliers that are not obvious names yet or something else?
And how do you distinguish a company that is genuinely exposed to the theme from one that is simply being associated with it because the narrative is popular?
I’m curios about the actual research process people use here, especially when the theme is still relatively early.
Thanks