The excellent answer to What ever happened to the Asteroid Redirect Mission? carries a warning:
There is no way to decouple politics from this; I have tried to be objective.
and it's possible an answer to this question will also need a bit of caution, while DSCOVR provides several kinds of data, the current US administration proposed to specifically de-fund it's Earth-facing camera EPIC several years in a row.
EPIC dates back to the original mission for DSCOVR more than 20 years ago. NASA proposed the mission, then called Triana, at the request of Vice President Al Gore to provide that full view of the Earth. The mission was put on hold early in the administration of President George W. Bush, with the spacecraft put into storage. The Obama administration resurrected the mission under the DSCOVR name and with a new emphasis on space weather monitoring.
The Trump administration proposed terminating EPIC operations. Its NASA budget requests for fiscal years 2018 and 2019 included no funding for EPIC, proposals that did not affect the overall DSCOVR mission, funded by NOAA. Congress rejected those proposals, explicitly including funding for DSCOVR operations in their final appropriations bills. The fiscal year 2020 NASA budget proposal did request $1.7 million for EPIC operations.
Wikipedia's Deep Space Climate Observatory says
In 1999, NASA's Inspector General reported that "the basic concept of the Triana mission was not peer reviewed", and "Triana's added science may not represent the best expenditure of NASA's limited science funding".8 Members of the U.S. Congress asked the National Academy of Sciences whether the project was worthwhile. The resulting report, released March 2000, stated that the mission was "strong and scientifically vital".9
Question: Were there any specific changes to the spacecraft's mission or design that led to the change from "...may not represent the best expenditure of NASA's limited science funding" to "strong and vital"?