So, in a nutshell: the WHO was about to undertake an initiative that would have harmed the tobacco companies. The tobacco companies, in turn, hired shills to attack the WHO. They presumably hired some to attack the WHO’s tobacco initiative, but they also hired people to attack other things the WHO was doing in order to discredit it more generally. Thus, the attack on Rachel Carson.
The real heavy lifting is here. What won’t these people do for money?