Some Core developers work for Blockstream. Some people say they want small blocks so that you will be forced to use Blockstream products (sidechains) to use bitcoin.
Some say Bitmain uses ASICboost for a 20% benefit on their mining operations - a huge advantage in the mining world of thin margins. Some say they don't want segwit because it would hinder ASICboost.
At the time of writing, mining fees constitute about 20% extra income on top of the new coins that miners mint. However, several companies have already switched from Bitcoin to Ethereum because of the high fees. Higher prices is good for business, but losing customers not so much. Miners may want just the right amount of scaling, to maximize income.
People also don't agree on what Bitcoin should be. Some want every human being (and computer) to be able to use Bitcoin directly. Others want Bitcoin to be a settlement network used only by big financial institutions, while regular people use something else. For everyone to be able to use Bitcoin we'd need scaling in a huge way. For a settlement network you don't need further scaling, which is what we are seeing so far. You may think that since individuals and small companies are leaving bitcoin, this means the settlement supporters are winning. However, noone is using bitcoin for settlements and there are no signs that this will change.
Then there are people who want bitcoin to fail. Whether it is because they invested heavily in an alt coin or because they benefit greatly from the status quo of the economy. As long as bitcoin is unable to support a growing user base, these are the people who are winning.
There is also the possibility that many of these people are just idiots who don't understand the benefits of cooperation. As the saying goes, don't attribute to malice what can be attributed to incompetence.