Standard Oil did a lot that was forward-thinking business. For example, oil shipped in barrels - real wooden barrels. Standard Oil got in the barrel-making business because they were having trouble getting enough barrels to run their business. (Today we call that "vertical integration"; they probably just thought of it as doing what they needed to do to keep their business running.) You don't build a business like Standard Oil just by being evil. You have to be able to execute really well.

But Standard Oil did a lot that was shady, too. For example, they shipped so much oil (by rail) that they demanded a kickback from railroads, or they'd take their business to the competing railroad. (This was back when there were enough railroads that there was competition.) That means that Standard Oil was paying lower freight rates (net) than other oil companies. (I think at this time rail rates were controlled by the government, so the kickbacks were probably illegal from that standing, not just from the extortion involved.) Standard Oil then went a step further. They demanded kickbacks not just for their own oil traffic, but for their competitors' oil shipments as well.

If you were a competitor, you weren't going to be able to prosper in that kind of an environment. Then Standard Oil would offer to buy your business...