Neither of those actions are illegal per se, but just because you it's not illegal to dictate terms doesn't mean you're allowed to choose any terms you want.
The problem here is that Google allegedly dictated terms that gave them an unfair advantage in an unrelated market, breaching EU antitrust law.
A stricter antitrust law might have prevented them from gaining such a dominant position in the first place, but that doesn't seem to be the issue here.
IF Google had manufactured all of the phones themselves, and had never open sourced Android, then they could have kept Chrome and Search on Android, and there would have been no problem, right?
But because Google let other people manufacture Androids, and because Google open sourced Android, now it's a problem?
Google didn't write all of Android, there are GPL components. They didn't have the choice to keep it closed source, all of it anyway.
And secondly, they're not being punished for having an open source operating system. They're being punished for forcing manufacturers to install their suite of software (simplified). It's not because they open sourced Android. I repeat, it's NOT BECAUSE THEY OPEN SOURCED ANDROID.
The terms wouldn't prohibit Samsung from making phones with another OS.
The terms would say that Samsung installs the version of Android 2 (the new and closed source one) that Google tells it to. As manufacturing partners are always told what to do.
No, Microsoft was fined for forcing OEMs to install IE and not preinstall other browsers on PCs if they wanted Windows. It had nothing to do directly with end users.
The problem here is that Google allegedly dictated terms that gave them an unfair advantage in an unrelated market, breaching EU antitrust law.
A stricter antitrust law might have prevented them from gaining such a dominant position in the first place, but that doesn't seem to be the issue here.