Are you sure that the advantage came from marketing? In my mind the advantage was that Chrome really was faster for example due to V8. Also can you explain why the "thus they should prefer Chrome" reasoning is flawed?
Personally, I haven't seen Google act in a way that prevents competition in the browser space (ie. being anticompetitive). If anything, Windows is more anticompetitive because it is closed source, making it much more difficult to create a competing product. All the web specifications are completely free. And Apple is the only vendor that prevents browser competition on their platform, although Windows does give you a popup telling you not install Chrome.[0]
The Google search agreements between Apple and Google seem more likely to be anticompetitive.
[0] Searching for Google Chrome with the default Bing search engine with the default Edge browser gives you this result:
>Promoted by Microsoft
>There's no need to download a new web browser. Microsoft recommends using Microsoft Edge for a fast, secure, and modern web experience that can help save you time and money.
See also Every trick Microsoft pulled to make you browse Edge instead of Chrome - https://www.theverge.com/23935029/microsoft-edge-forced-wind...
There were feature differences for sure, but the marketing did a massive amount of work in this case. If people switched for features, all that spending for years wouldn't be necessary.
If the answer to any of those is no, it’s more than simple advertising.
I feel like it should be illegal to use your profits in one industry to run a loss leader in a totally separate industry.
There’s nothing wrong with running a loss leader, only with squeezing everybody else out.
Most of that advantage comes from an unfair practice, of Google making consumers think that their choice of browser was in someway inferior (which could be true) and thus they should prefer Chrome (which is not true). If Chrome won market dominance using this method, then it becomes an unfair practice. Same thing with Microsoft Edge, Apple's App Store, etc. You can't use your market power in one market to influence another.