I won't go into details but you seem to be assuming specific, relatively unsophisticated methods. Also, not everything you mention is available or useful and it's not close to enough to for more sophisticated frauds.[1][2] Keep in mind that most ads are paid on a per-impression basis - the main reason to simulate clicks is because at some point people will notice if a specific site consumes a bunch of impressions but doesn't contribute any clicks. Ad-tech companies tend to be competent in ML since it's necessary for optimization, but fraud remains a hard problem.
It's unclear any decision they made mattered at all. Building a Windows mobile app made no real sense and even the largest app developers had trouble justifying the investment. Also, I don't think Microsoft stood to gain all that much even if they were able to gain a foothold in the market.
I'm not sure what it is that you think Microsoft did with IE but Google is doing pretty much the same, in the sense that their app ecosystem is all-or-nothing. And even worse in the sense that it's tied to the cloud account - back then, you didn't need a Microsoft account to use Windows.
Advertisers are not complaining - they can vote with their money. It's the publishers that are hit by making ads harder. Without allowing publishers to monetize, content will move behind paywalls or closed ecosystems (as opposed to open web) that do make ads easier. Also, over time, browsers that make it impossible to monetize will likely to be banned by publishers - this already started to happen, with some publishers not allowing incognito mode, etc.
Also, maybe I'm missing something but I don't see how this addresses fraud and any advertising solution that doesn't address fraud is basically DOA. How do they ensure that clicks and conversions are legitimate? It's already a hard problem, despite the large amounts of data that legitimate browsing activities leak.
[1] https://www.buzzfeednews.com/article/craigsilverman/porn-run...
[2] https://clearcode.cc/blog/rtb-online-advertising-fraud/