Why do all sheets in workbooks get hidded when finished running the VBA code?

Question

I am using the below code to loop through all workbooks in a chosen folder and change some content in Sheet1 of each workbook. But when the code is finished, the content is successfully changed but all sheets are hidden. Not sure why and how to fix it?

Sub LoopChangeCoreName()
    Dim wb, newwb As Workbook
    Dim myPath As String
    Dim myFile As String
    Dim myExtension As String
    Dim FldrPicker As FileDialog
    Dim i, m As Integer
    Dim LR As Long
    Dim r As Integer
    Dim rng As Range
    Dim AuthorName As String
    Dim CoreName As String
    
    'Optimize Macro Speed
    Application.ScreenUpdating = False
    Application.EnableEvents = False
    Application.Calculation = xlCalculationManual
    
    'Retrieve Target Folder Path From User
    Set FldrPicker = Application.FileDialog(msoFileDialogFolderPicker)
    
    With FldrPicker
        .Title = "Select A Target Folder"
        .AllowMultiSelect = False
        If .Show <> -1 Then GoTo NextCode
        myPath = .SelectedItems(1) & "\"
    End With
    
    'In Case of Cancel
NextCode:
    myPath = myPath
    If myPath = "" Then GoTo ResetSettings
    
    'Target File Extension (must include wildcard "*")
    myExtension = "*.xls*"
    
    'Target Path with Ending Extention
    myFile = Dir(myPath & myExtension)

    'Loop through each Excel file in folder
    Do While myFile <> ""
        Application.ScreenUpdating = False
        'Set variable equal to opened workbook
        Set wb = GetObject(myPath & myFile)
        
        'Ensure Workbook has opened before moving on to next line of code
        DoEvents

        If InStr(myFile, "_") > 0 Then AuthorName = Split(myFile, "_")(0)
        For m = 2 To wb.Sheets(1).UsedRange.Rows.Count
            CoreName = AuthorName & "_" & wb.Sheets(1).Range("A" & m).Value
            wb.Sheets(1).Range("A" & m) = CoreName
        Next m
                
        DoEvents
          
        'Save and Close Workbook
        wb.Sheets(1).Visible = True
        wb.Close SaveChanges:=True
          
        'Ensure Workbook has closed before moving on to next line of code
        DoEvents
        'Get next file name
        myFile = Dir
    Loop
    
    'Message Box when tasks are completed
    MsgBox "Task Complete!"
    
ResetSettings:
    'Reset Macro Optimization Settings
    Application.EnableEvents = True
    Application.Calculation = xlCalculationAutomatic
    Application.ScreenUpdating = True
End Sub

(repeat only to pass the post check) I am using the below code to loop through all workbooks in a chosen folder and change some content in Sheet1 of each workbook. But when the code is finished, the content is successfully changed but all sheets are hidden. Not sure why and how to fix it? Thank you so much.