Funding and time isn't all of it.
If, for example, type I diabetes wasn't a common condition, and you had a handful of patients with it, you could work out the mechanism with several hundred dollars worth of tests, and several standard biochemistry textbooks.
CFS, unfortunately has a mechanism which seems to involve lots of poorly understood parts of the body working together. Further, there are no simple tests for it.
We obviously don't know what insights might lead to a cure, but there are some hard dates.
For example, if Rituximab turns out as well as hoped in a subset of patients, that couldn't have happened before some years after it was invented. (1997+)
If the microbiome is the key, it couldn't have happened much before 2008, as the technology wasn't available.
Some investigative techniques that have been used are even newer.
Unless it turns out that there is a simple theraputic that happens to work without deep understanding (rituximab), in order to understand a disease, you need to know how the mechanism of the disease works. How much time and money this will take depends on how complex the disease is, and the available tests.
Just throwing money at something doesn't fix it. For example, HIV, many billions have been spent trying to come up with a cure, rather than a treatment, and that is 'just' a virus with a well understood mechanism comparative to CFS.
Having said that, even with no idea whatsoever about mechanism, useful research that has not been done, could have been, relatively inexpensively.
For example, longitudinal monitoring (at least weekly) of a cohort of CFS patients.