This article explains the reason for the move from compassionate use to expanded access.
Quote from the article:
The compassionate use process was set up for "very limited access" to drugs before Food and Drug Administration approval, not for the deluge of requests it has received during the COVID-19 pandemic, Gilead said in its statement.
Going to expanded access effectively cuts the through the red-tape and allows more patients to have access to remdesivir and they will gain access to it more quickly.
Quote from the article:
Gilead said the decision ultimately will allow the company to process and manage emergency use of the drug more efficiently.