Comment by mb2100

That's because on mobile, PageSpeed (which is a hosted version of the Ligthhouse dev tools you also have in Chrome) simulates a low-end Android device on a slow 3G network, which is what a lot of website visitors actually use (as opposed to the web developer using the newest iPhone on great WiFi).

That's why content-driven websites should not be an SPA, and why I built https://mastrojs.github.io