If some search engine came and produced vastly superior results to Google, people would absolutely switch. That's how Google came to power in the first place: their results were just better.
Not sure what we can be expected to do. Split up Facebook and everyone will eventually flock to 1 maybe two services. Split up Google and you take away the majority of "free to use" apps because those are dependent on Google's advertising.
True, although that's unlikely to happen any time soon. (then again, how can we really predict any of this)
> That's how Google came to power in the first place: their results were just better.
That was also back when the barrier to entry was much lower, and there was a lot of low-hanging fruit for Google to pick both in search and other areas.
Let's say that someone today manages to get enough money and talent to build something that is at least equivalent to Google: I think people will overwhelmingly stick with Google because of the brand recognition and because "everyone else uses it." As both services would be free to use, there's nothing to force people to closely consider what merits their dollars will be spent on. Google could be highly censored and totally corrupt in other ways, but people will continue to use it because, as their wallets aren't being punished or used for nefarious purposes, they'll be willing to put up with seemingly benign abuse that they feel they have no part in perpetuating.
This is one reason why, even though I am not against advertising in and of itself, I despise what the state of digital advertising has done to the web and the world depending on it. And, as you stated, Google's advertising platform enables them to have many tentacles without the inherent need to own other companies; instead, they can have individuals businesses they don't own depend on their applications funded by ad revenue, making it a tremendously difficult choice for policy makers to split them up.
It might not be prevented or restricted in the traditional sense, but the barrier to relevant market share has become nearly impossible to cross. The alternatives you cite, besides maybe DDG, aren't serious contenders to Google or Facebook.
Now, perhaps they would be if people paid to use those services, then they'd be more likely to pick and choose between the selection because they're going to want to pay for the right one for them, not necessarily the one that everyone else is using. But because the internet is largely ad-funded, hence nobody has to pay for most immaterial things, they're free to flock to wherever the crowd may be. That's why it's particularly bad that Facebook and Google are such "monopolies", even if the word doesn't exactly fit the situation. To compete with these services, you can't just appeal to a person's sensibilities within a market. DDG might be an exception, but it hasn't been around long enough for us to tell whether it's just a fad or will be quickly stamped out by something else.