Organize values on X-Axis

Rewrite it like this and ensure that there isn't aggregation on the sort, in the screenshot you have it set to COUNT. It should look like this:

CASE WHEN `split_detail` = 'CEO' THEN 1
WHEN `split_detail` = 'Head of Business' THEN 2
WHEN `split_detail` = 'key management personnel(KMP)' THEN 3
WHEN `split_detail` = 'Other Executives/general managers' THEN 4
WHEN `split_detail` = 'Senior Managers' THEN 5
WHEN `split_detail` = 'Other managers' THEN 6
ELSE 7 END

Yeah it is because the values are case sensitive. So in the beastmode it doesn't find a match for "Senior Managers" because the "M" is capitalized in the case statement but not in the data, so it places it in position 7 from the ELSE part of the statement. A great way to protect against this is to wrap the values in LOWER() and then type out the text values as all lowercase.

CASE WHEN LOWER(`split_detail`) = 'ceo' THEN 1
WHEN LOWER(`split_detail`) = 'head of business' THEN 2
WHEN LOWER(`split_detail`) = 'key management personnel (kmp)' THEN 3
WHEN LOWER(`split_detail`) = 'other executives/general managers' THEN 4
WHEN LOWER(`split_detail`) = 'senior managers' THEN 5
WHEN LOWER(`split_detail`) = 'other managers' THEN 6
ELSE 7 END

One other suggestion would be to change the chart type to be a 100% stacked bar since you are comparing two % values that will always sum to 100%. Line charts are typically used to show trends over time.