Now - Chrome is slower vs Firefox Quantum's new privacy because of the ad networks. The ad networks have had no incentive up until now to improve their shitty code.
If people start switching to Firefox and turning on privacy more to get faster browsing - they will lose the game entirely.
All that's needed is for a modest uptick in usage of this mode and for some ad networks to get scared. They spend some of the pile of money they swim in to not ruin everyone's browser experience and bam - we get a less crappy internet.
If they don't shape up - then we get a faster internet with better privacy. Even better.