It would be trivial for them to build a Chromebook, or Android phone, or browser that you can't flip into dev mode, but they've never done that, even though many of their competitors in the space regularly lock users out of their devices.
In a world with attestation, you can't browse any website unless you are using Chrome or another attested browser. The New York Times would refuse to serve content to unattested user agents. That is what would make everyone use Chrome.