This doesn't surprise me at all. It took almost 40 years to prove that smoking causes lung cancer. Similarly, despite unambiguous scientific evidence, it still seems acceptable to deny that man-made CO2 release into the atmosphere causes global warming. There's actually a good book covering these two instances and others: "Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke…
Common factor: Money to be made. Tobacco was the core of many states' economies, and still remains a massive industry which makes many people wealthy. Dealing with CO2 emissions would have required dealing with fossil fuel use... and that's tons of money and power in play there. Sugar is, at the very least, another substance people crave, and has been making people rich for hundreds of years. Delaying tactics are fea…
This is actually quite difficult. Despite its shortcomings (and perhaps ironically) religion can be effective at convincing people to put others first but I would say the default behavior in most people is "I only care about myself and family first". This default behavior is exacerbated when people follow the influence of greed, lust, etc.