The planning commission decision was on whether this particular mega-development should move forward and basically consume all of the county's planning time and resources for the next 3-5 years. The commission rightly said no. The vote was NOT about authorizing studies; it was about authorizing the process that would lead to this mega-development's approval.
Now, you can look at the offer by the developers to pay for the studies needed to permit their development in several ways:
1. Nonsensical. These sorts of studies must be performed; of course the developers should pay for them. They benefit no one else.
2. A clever attempt by the developers, once they saw the massive public opposition and read the writing on the wall, to change the subject.
3. A clever attempt to hijack the County's planning process. This is a common ploy by large developers. They pay (at least partially) for the studies. The consultants must be acceptable to the developers. He who pays the piper calls the tune.