I want to share another solution/measure that works:

Share% = 
VAR denom = CALCULATE(
    SUM(Table1[Value]),
    ALL('Table1'[Financial KPI]),
    'Table1'[Financial KPI] = MAX(Table1[Denominator])
)
VAR num = CALCULATE(
    SUM(Table1[Value]),
    'Table1'[Financial KPI] = MAX(Table1[Financial KPI])
)
RETURN
    DIVIDE(
        num,
        denom,
        0
    )