How to import a large batch of CSV into a Google spreadsheet with each CSV file being its own separate sheet. The sheet is named after the CSV file it is sourced from.

import-csv-from-drive-folder.gs

function convertCSVFilesToSheets() {
  var folderId = "DRIVE_FOLDER_ID"; // Replace with the ID of your folder
  var spreadsheetId = "SHEET_ID"; // Replace with the ID of your spreadsheet

  var folder = DriveApp.getFolderById(folderId);
  var files = folder.getFiles();

  var spreadsheet = SpreadsheetApp.openById(spreadsheetId);

  while (files.hasNext()) {
    var file = files.next();
    if (file.getMimeType() == "text/csv") {
      var csvData = file.getBlob().getDataAsString();
      var csvLines = csvData.split('\n');
      var sheet = spreadsheet.insertSheet(file.getName());

      for (var i = 0; i < csvLines.length; i++) {
        var rowData = csvLines[i].split(',');
        sheet.getRange(i + 1, 1, 1, rowData.length).setValues([rowData]);
      }
    }
  }
}

To use.
Upload files to a folder in Google Drive.
Get the ID of the folder. It is in the share link.
Make a new spreadsheet.
Get the ID from the URL.
Go to Extensions. Choose App Script.
Paste the above code.
Edit and replace the drive folder id and sheet id with the IDs you copied earlier.
Save.
Run.
Give it permissions when asked.
Wait.....
Enjoy.