It was not. Serbia was establishing order within its territory when NATO bombed it without any approval from the UN, basically doing something just because they could. Remind you of anyone?
In a way, they were implementing a century old policy of a guy named Vaso Cubrilovic who argued that Albanians should be expelled[2] from the lands Serbia (precursor of Yugoslavia) took in 1913.
What NATO did, is stopping exactly this from happening.
[1] https://www.hrw.org/report/2001/10/26/under-orders/war-crime...
[2] https://en.m.wikipedia.org/wiki/The_Expulsion_of_the_Albania...
And as for that supposed policy of Albanian expulsion, by how much did the percentage of Albanians diminish during the Serbian rule of Kosovo? And by how much did the number of Serbs diminish during the Albanian rule of Kosovo?