20 years ago businesses bought the .org for whatever trademarks they owned to stop someone else grabbing it. Same for .com (which they used) and .net. They usually pointed all three domains to the same place. That activity has stopped. There will be far fewer .org domains sold today because businesses have stopped doing that.
As someone who owns .org domain names. That might be what it's for like .com is for commercial and .net is for networks. However that is not at all how they're used.
Perhaps by some percentage of them are registered non-profits. However not the majority.