And location and one's own territorial ambitions affect this too. If Germany annexed the Netherlands and Belgium, but opposed the Russians, the Ottomans would not necessarily say "Whoa, Germany's way too belligerent for us to work with!" Now, if they annex one of the Turks' neighbors, like Greece, that starts getting scary, but it's all about location. In Victoria, if Japan takes Russian Siberia and annexes Korea in one go, it's a pariah, and that might make sense with consciously interventionist powers like the UK whose interest was very much in the status quo, because they ruled things. But who's to say that, again, the Ottomans wouldn't ally with a similar power whose star is rising over Asia--and who is far too distant at the moment to pose a threat?
Alliances ought to be marriages of convenience, as they are in life, rather than the nice guy's clubs they become in Victoria. And don't even get me started on that one war I fought against Peru. Ecuador nearly doubled in size and I took a few provinces too, but that was enough to make the allies who'd glutted on Peruvian blood to turn their back on me. I was no longer a nice guy, evidently, even though I was a terrific warmaker. Then we all got picked off by Brazil, who should have frightened us far more than any one of our now collapsed alliance.