The core motivation wasn't speed -- it was ads. Chrome was designed to send people to Google Search instead of websites. The address bar auto-completion in Firefox would always suggest actual URLs, but Chrome's would send people to Google Search to click on ads on the way to their desired destinations. The ads started to become camouflaged so that most users couldn't tell them from organic results, and Google continued to make the ads harder to distinguish over time. I'm sure that Google also had long-term worries about ad-blocking and wanted to control the browser.

"We just want to make the Web faster" is what they tell their employees so that otherwise ethical people will write code that does unethical things. (AMP/portals is another example.)