[wonders]

---how did the Christians in Kosovo became minority?---

You skipped over some important parts. Like WWII. That's when the pro-Nazi ethnic Albanians of Kosovo slaughtered and drove huge numbers of Serbs out. Then Tito wouldn't let the surviving Serbs go back to their homes in Kosovo. And he looked the other way as Albanians poured into Kosovo from his buddy Enver's stalag. There followed more abuses against Serbs, more Serbs fleeing the province. Meanwhile, residents of the rest of Yugoslavia had to pay a surtax to support the welfare state of Kosovo. Didn't make for happy relations, to say the least.

[FormerLib]

wonders posted some details that you conveniently overlook as well:

You skipped over some important parts. Like WWII. That's when the pro-Nazi ethnic Albanians of Kosovo slaughtered and drove huge numbers of Serbs out. Then Tito wouldn't let the surviving Serbs go back to their homes in Kosovo. And he looked the other way as Albanians poured into Kosovo from his buddy Enver's stalag. There followed more abuses against Serbs, more Serbs fleeing the province.

[Ronly Bonly Jones]

---how did the Christians in Kosovo became minority?--->>>

They up and left because it's a poverty-stricken schitehole. The Albanians moved in only because it's a moderately less poverty-stricken schitehole than Albania proper.