Strictly speaking, it is over the companies monopoly in search. Google also lives in other markets where there is competition, so this may be about those markets not search.
And, charity to the actual ruling, I'm assuming that better arguments were made behind closed doors to get to this point? I don't think it should be a problem to have parts of the process closed, at all. I do find it odd to have such a large blockout, though.
They don't - the judge determines what should be sealed by weighing public interest against potential harm. In this instance, the article author disagrees with the judge's decisions.
I think it is fair to question judgements of people. Even judges and article authors.
Do we have any way of assessing how fair these judgements were? Do you have any way of showing that the DOJ was trying to get a "free ride" on revealing trade secrets?
For example, Apple maybe had an auction to bid for default search spot on their platforms. Google bid the highest as we know, but we don't know what the competition bid and Google probably want to present that as evidence that this was just a normal auction similar to bidding for advertisement spots. For example, if Bing bid 90% of the current Google bid, then it is pretty clear that Google wasn't paying Apple to keep competition out but rather paying Apple for a premium spot in a fair market.
Nobody argues that Apple is anti competitive when they pay Google to put ads on top of certain search results, so why would Google be anti competitive when they pay Apple for a premium spot? They don't pay Apple to keep others out, just for the premium spot, you can still use other search engines.