Consider in the 90s and early 00s. Soicity still considered saying "thats gay" to basically everything as a standard normal and entirely fine thing. Regardless of context or intention. So the plight of gay communities was basically invisible to the avg person. Most people didn't know what a transperson was, or even really cared or knew that gender identity was a thing. If they did it was so far from what anyone talked about that it basically didn't matter.
Everything was focused towards things like 9/11 and other major events that happened at the turn of the century that affected not only the US, but in turn caused drastic effects the world over by what the US then proceeded to do. Not to mention other regions and their notable events during the era.
The rise of the internet didn't really happen for the avg person till 2010 and beyond, for the most part till DSL became standard the idea of social media was only for the small handful of people on IRC, fourms of the 00s. Which was mostly high schoolers and college kids, outside of the older folk that where entrenched in nerdy industries or hobbies which was few and far between.
So unless you personally knew people, all you really got was typically third or fourth hand information or what you picked up from reading maganizes in the check out at the store. For the most part the way infomation traveled didnt change in any meaningful way from around 1920 with the rise of the telephone till 2008-2010 when facebook finally reached its peak and was more then just the exodus of myspace kids, and the elders and parents started using it.
The idea of a inter connected world where you really know all this infomation about celeberities or really ANYTHING about people over seas beyond headlines. Has only been around for honestly? About 10-15 years.
From like the middle ages till 1840, anything beyond the next town over was the limit of infomation. From 1840 to 1920 you could have important infomation reach a small country. From 1920 to 2010 you could reach a nation of people one at a time. But from 2010 onward every person in the world can see anything about anyone at any time.
Basically every question along the lines of what you asked boils down to one simple thing. Communication between people for all of history was EXTREMELY limited. Connecting people makes it hard to hide. No longer can you wear a mask for a single interview, or lie to a reporter, move to the next town over. Suddenly become a new person.
Now your entire life follows you for all of your life. In all of human history that is NOT normal for 99.999% of people. All the other whys and hows and excuses all boil down to just taking advantage of this lack in communication. Oh someones racist but its too your advantage to let them? Then let them, cause whos going to find out. No one that would personally effect you! But today? That doesn't happen with out PR problems. Minorities of all types now have voices, and their allies can see and send help.
Communication, is the single biggest if only core factor. The lack of it breeds problems, the over abundance provides relief.