Context from Wikipedia (because the article doesn't have it):
"The main combatants were Azerbaijan, with support from Turkey and foreign mercenary groups on one side; and the self-proclaimed Republic of Artsakh and Armenia, on the other. It was the latest escalation of an unresolved conflict over the region, which was annexed to Azerbaijan during the Soviet era and internationally recognized as part of Azerbaijan, but partially governed by Artsakh, a breakaway state with an Armenian ethnic majority."
It was 90% Armenian in the 1920s; the Azerbaijan SSR promoted immigration of Azerbaijani in the region between then and the 1980s, but it never went below 75%.
30 years ago isn't that long - there are still people alive in Azerbaijan who own property deeds for houses in Karabakh, and who were born and grew up there. At the time there were 684k displaced Azerbaijanis (UN number), most of which are still alive today.
"The main combatants were Azerbaijan, with support from Turkey and foreign mercenary groups on one side; and the self-proclaimed Republic of Artsakh and Armenia, on the other. It was the latest escalation of an unresolved conflict over the region, which was annexed to Azerbaijan during the Soviet era and internationally recognized as part of Azerbaijan, but partially governed by Artsakh, a breakaway state with an Armenian ethnic majority."