I watched the BBC documentary "The death of Yugoslavia" which was recommended to be as being a neutral source.
When he first turned against Croatia after annexing Kosovo, the other leaders of the council seemed to back him up, including Izetbegović of Bosnia and Herzegovina. Why did they not see that Milosevic would inevitably turn against them and would not respect the sovereignty of any country with a large Serbian minority?
Also: Why were they ok with Serbia playing such a major role in the whole of Yugoslavia, being the capital of both and having control over the biggest part of the federal military?
Because people tried to avoid the war. He was allowed to get out of hand in the same way allies allowed Hitler to get out of hand trough appeasement. Izetbegovic especially did the most he could to avoid war, including sabotaging his own side and giving up weapon stockpiles to Serbs.
No one was OK, but what could they do? Macedonians were a non factor, Slovenians didn't care, Croats were still being shamed by Ustasha's and Bosnia couldn't do a single thing. Montenegro supported Serbia. Tito when he held power ensured that most power lay with Serbia. He tried to control it by putting weapon industry in Bosnia, banking in Slovenia and electronics in Croatia and giving states and outonomous regions a single vote. Milosevic used that by gaining control over Kosovo and Vojvodina, ensuring Montenegrin support. Those are already 4 votes in his hands.