I appreciate that there is a certain sense of accomplishment that comes with doing something 'from scratch' but why wouldn't you use https://phaser.io/ or any of the other libraries/frameworks for HTML5 development? It's built for almost exactly this type of game.
Does anyone know if there is a framework for turn based strategy for HTML5? Phaser seems to have more of a real time and physics focus.
Phaser is just an all purpose 2D game engine, what kind of game you create doesn't matter. It gives you a lot of tools and functionality you're probably going to end up creating yourself if you used something that's just a rendering engine like Pixi.js instead. Phaser <=2 was built from Pixi.
OP didn't really build this from "scratch" in the strict sense, they used Three.js. This is kind of the 3D equivalent of Pixi.