Sum all individual Columns for large data sets

I think the simplest approach for you is:

1. Leave your CV query as is, where it just focuses on querying data source files, parsing, combining, etc.
2. Right-click on your CV query, select Reference
   (this will create a new query where your first step, Source, is just pointing to CV)
3. On your new query (rename to whatever), open the 'Advanced Editor', replace all text with a solution from here, just be sure that your Source step is referring to your original query, CV
4. Most likely, you will want to turn off load on CV, so only the new table in desired output is added to your model and/or sheet

lbendlin's solution should work for you IF your columns are data type text and the only value you want to sum across all columns is "1" (as text).

In case your CV table has number/integer data typed columns, you can instead use the below code, following same approach, which is: 1) unpivot all columns, 2) extract group text between _'s, 3) pivot values back and sum

let
    // Reference to the original table
    Source = CV,
    // Unpivot all columns. Column names go to the "Attribute" column,
    // and values go to the "Value" column.
    UnpivotCols = Table.UnpivotOtherColumns(Source, {}, "Attribute", "Value"),
    // Extract your group text/labels from between the first and second _
    ExtractGroupText = Table.TransformColumns(
        UnpivotCols, {{"Attribute", each Text.BetweenDelimiters(_, "_", "_"), type text}}
    ),
    // Pivot the table back, summing all values under matching group labels
    PivotValueAndSum = Table.Pivot(
        ExtractGroupText, List.Distinct(ExtractGroupText[Attribute]), "Attribute", "Value", List.Sum
    )
in
    PivotValueAndSum

Here is a quick gif of the steps I outlined at top. Note: this is in PBI Desktop, not Excel, so UI may be a little different, but everything should apply the same, mostly.