NSIS issue: How to get input from user while setup and use it inside the application?

[VueMe2020]

While adding a script to run in the process of installation, I see the file I'm writing into being deleted or removed from the installation directory. Why?

my vue.config.js file:

pluginOptions: {
    electronBuilder: {
      builderOptions: {
        appId: 'test.com',
        win: {
          "target": ["nsis"] 
        },
        "nsis": {
          "include": "build/installer.nsh",
          "oneClick": false,
          "allowToChangeInstallationDirectory": true
        }

      }
    }
  }

my script create new file and write inside user name/password:

my installer.nsh file:

!include nsDialogs.nsh
!include LogicLib.nsh

XPStyle on

Var Dialog
Var UserLabel
Var UserText
Var UserState
Var PassLabel
Var PassText
Var PassState

Page custom nsDialogsPage nsDialogsPageLeave

Function nsDialogsPage

    nsDialogs::Create 1018
    Pop $Dialog

    ${If} $Dialog == error
        Abort
    ${EndIf}

    ${NSD_CreateLabel} 0 0 100% 12u "Your Username:"
    Pop $UserLabel

    ${NSD_CreateText} 0 13u 100% 12u $UserState
    Pop $UserText

    ${NSD_CreateLabel} 0 39u 100% 12u "Your Password:"
    Pop $PassLabel

    ${NSD_CreatePassword} 0 52u 100% 12u $PassState
    Pop $PassText

    nsDialogs::Show

FunctionEnd

Function nsDialogsPageLeave

    ${NSD_GetText} $UserText $UserState
    ${NSD_GetText} $PassText $PassState

    ${If} $UserState == ""
        MessageBox MB_OK "Username is missing."
        Abort
    ${EndIf}

    ${If} $PassState == ""
        MessageBox MB_OK "Password is missing."
        Abort
    ${EndIf}

    StrCpy $1 $UserState
    StrCpy $2 $PassState

FunctionEnd

Section

  SetOutPath "$INSTDIR\myfolder" 
  FileOpen $9 $INSTDIR\myfolder\credentials.txt w
  FileWrite $9 "$1 $2"
  FileClose $9
 

SectionEnd

While running the setup.exe file I can see it creates "myfolder" and also creates the "credentials.txt" file and update it, but when the process ends - the folder stays empty. The file was removed. Why? What I'm missing here?

Is there a better way to update some file in the setup process and use that info inside the application? the user name and pass for example are something needed to be used inside the application.