History doesn't show that though. It shows Croatia and Serbia invading Bosnia to take it over completely. Not just after 1991 but even back during the days of monarchs (Hungary and Byzantine even fought for these lands and people).
The ethnic cleansing in Bosnia did not come before the wars. I believe they were a result of invasions on Bosnia which forced all 3 ethnic groups to scatter. Otherwise today there would be hundreds of thousands of Serbs remaining in Croatia, an additional hundreds of thousands of Serbs and Croatians remaining in Bosnia, and hundreds of thousands of Muslims remaining in Serbia.
There doesn't seem to be suggestive evidence that prior to 1991 that the 55-60% Bosnian population wanted to boot out the 40-45% total population of Croats and Serbs. This would be very suicidal and they would have never attempted such a thing.
Remember, there were considerable amounts of Orthodox Bosnians/Bosnian Serbs, and other none Bosniak minorities that fought against the Serbian invasion. You can read about them in news articles and documentaries.
It actually does show that to be the case. Serbs were the majority of the population on approximately 2/3 of Bosnia's territory. That's because they were agricultural pastoralists or farmers while Muslims had privileges to live in cities as landlords or artisans. Croats were somewhere in between in terms of their urbanization. So that fact that the Serbs held 70% of Bosnia at one point doesn't imply that they conquered most of that territory from people who were previously the majority on it (some they did, most they did not).
The ethnic cleansing was a spontaneous result and strategy of a conflict where nobody could trust their own neighbor. To preemptively prevent them from waging guerrila war, they expelled most and killed some.
The ethnic cleansing by Serbs and Croats was more *visible* than by Muslims because they did it over larger tracts of territory (e.g. villages or towns that were mixed or heavily Muslim surrounded by predominantly Serb or Croat villages). Muslims engaged in silent ethnic cleansing of towns and cities, whereby 15% or 20% (or 40% in the odd case) of Croats or Serbs or both were simply driven to flee due to the reign of terror Muslim warlords conducted from within.
Serbia hasn't expelled Muslims - as a state policy - since the 1800s. In the 1990s there were no expulsions of Muslims out of Serbia. There were two incidents of massacre perpetrated by a Bosnian Serb warlord against Serbian Muslims (Sjeverin and Strpci), and in one case he invaded Serbia and seized passengers off a bus and in the other he attacked a train going between Belgrade and Montenegro (passing through Bosnia) and took off more passengers.
Bosnian Muslims were never 55% or 60%. It's the Bosnian Christians who are 55-60% (together). The Muslims are 45-50%. They are not a majority. Which makes their attempt to hijack control over all of Bosnia the more insane and unfeasible.
There were a few Serbs in Sarajevo primarily who fought for the Muslims. Most did not. There were also Muslims who fought with Serbs (e.g. Fikret Abdic was allied with them). It proves nothing. The vast majority of each community was engaged in war with the other community.