Since Speckle adopted Vue, there have been several iterations of what React even is or where its focus has shifted in the This-is-the-definitive-best-way-to-build-a-react-app, whereas Vue has gone from Vue2 to Vue3. There were no doubt reasons, and ease of use was a key one. Ultimately, with the passage of time, this decision is somewhat moot.
We can look at a React tutorial or hold out hope that any of the active Speckle Community app developers outside our team share a tutorial or simply open-source their code. It would indeed be a valuable contribution.
I made a call out here: Help Us Build the Ultimate Speckle Viewer Tutorial