I learned React back in the class component days. I recently picked it back up and found functional components and hooks to be absolutely baffling. Does anyone know why they went down this route?

Trust me, the function based components are way too simpler. Just a function that returns HTML. That's it. compose your UI as those functions. These functions can take arguments to customise their output (rendered HTML) as arguments (called props) or can call special functions from React (called hooks) such as asking the React to "remember" a value for you (state) or cache something for you (useMemo) so as to not compute it every time or trigger rendering if value of certain variables change (useEffect) or at the component start (useEffect with no dependencies mentioned) and that's all the React that you need to know for I would say your 95% of the needs.

React compiler (already used for Facebook and Instragram code base) further renders the use of certain hooks unncessary thus making React a lot more simpler.

Hooks require less boilerplate to set up and reuse stateful logic across components

If you havent watched it yet, the talk that introduced hooks explains much better than I can: https://youtu.be/dpw9EHDh2bM