We started OWA with a group of primarily Safari first developers, in that iOS Safari is our primary target platform. We've had over a decade of major issues from rendering bugs, to lack of functionality to our apps breaking for months at a time waiting for a patch. The severe underfunding of Safari/webkit coupled with a ban on competition meant that it was never going to be viable to ship Web Apps to iOS. So the question is, how do you convince the worlds richest company to invest a extra few hundred million/year into their own browser?
The answer is competition. Competition provides Apple a deep incentive to produce a capable, feature risk browser at risk of losing users to the other vendors. Each 1% of Safari users is worth 150m/year in google search revenue, a number so large it would make even Apple take notice.
As web developers we see the value in having browser engine competition, many of us lived through the IE6 era and know the risks of the monopolistic competitive behavior like we're seeing from Apple (Side-point: At no point did Microsoft ever ban the competition).
The status-quo where Safari/Webkit was both stifling the Web and Web Apps and providing no competitive pressure on Chrome/Edge/Firefox + the severe underinvestment from Apple meant that a regulatory solution was needed.