So you don't understand the concept of abusing a dominant position.
Yes, at first sight your argument makes sense. But look at it another way.
Google is the dominant search engine - I don't think that's under dispute. Yes there are others, but Google is very dominant. Yes it got there by being better, but that's not the point.
As a business, Google search engine makes it's money from advertising - basically selling rankings/listings against search terms. So if I sell widgets, I can arrange that whenever anyone searches for widgets then my listing can appear in the advertising links. All that is fine.
Now suppose Google wants to get into the online widgets business. They can effectively give themselves a free ride to the top of the list. It's alleged that they are artificially boosting the price they charge me for my listings - so I pay more than I would if it was a fair auction for the use of widgets as a keyword. So immediately they have me paying more than I should be for getting seen in searches for widgets - that's the first offence.
Secondly, whether their online widgets are better than mine or not, they can (and it appears do) promote their own widgets service at the top of the list. If it was anyone else trying to get into the widgets business, they couldn't do this without outbidding me for the search keyword and getting to be a popular site - ie any other new competitor would have to compete to be the best widget provider and so get the sort of online linking that popular sites get.
But Google doesn't have to be the best to be at the top - they can give themselves that free ride. No 1 spot in the results - effectively buying market share since so many people will just click the first result.
The nearest sort of analogy (and I admit not very good) might be if there were a large commercial/retail park somewhere - and all the roads on it were private and owned by the park. Because it's a huge park, with lots of retailers, most of the local population shop there.
Now I own a widget shop, and I rely on those passing customers for business. Suppose the park owners decide they want the widget business. I pay for an advertising hoarding near the site entrance promoting my widget business - but the site owners put up their own hoarding so it partially obscures mine - and they put up signs all over the park with something like "Widgets - this way" and pointing to their own new widget shop.
I'll still get some business, but a huge proportion of potential customers will never find my shop. The park owners have used their dominant position (don't forget, nearly everyone comes here to shop because of it's size so just moving elsewhere isn't really an option) to deliberately to shove their own new business ahead of everyone else.
If it was fair then they'd have the widget shop as a separate unit that had to buy advertising space in exactly the same way as I do. Then they could compete on who sells the best widgets, who has the most polite staff etc. As it is, they can effectively cripple any business they want to take over the market for - simply by giving themselves a huge (and free) advantage, paid for by the rest of their business activities.
I suggest you read a bit of history on anti-competitive behaviour. There's plenty to look at - Standard Oil back in the 50's IIRC, then IBM with cash registers, Microsoft. In all these cases (particularly Std Oil and IBM, Microsoft used more technical methods), the company used cross subsidies and other techniques to effectively kill off competition by running one part of the business at a loss so they could undermine any competitors who weren't able to provide such cross funding.