I don’t know what’s on your Excel file and I don’t know what pd.read_excel does, so I don’t know what to fix.
But I’m guessing that your Excel file has a column with strings containing the representation of a list of names and you are writing that string (not that list of names that it represents) on the simple object column in Anvil.
Here l is a list of names, while s is a string that looks like the representation of the list of names, and can be converted to a list of names with the json.loads:
l = ['joe', 'mary']
s = '["joe", "mary"]'
print(json.loads(s))