Market share. Many web developers these days are bad at their jobs (or are ordered to be by their bosses) and only test things on Google Chrome, causing many we

Market share. Many web developers these days are bad at their jobs (or are ordered to be by their bosses) and only test things on Google Chrome, causing many websites to have issues on Firefox (the same happened to Trident) . Using Chromium as a base allows them to ride Google's market share and have almost all websites work with their browser.