MVC DropDownList retrieve model data

I'm trying to set the selected value of a dropdownlist from the database information.

I load a list from the controller:

public void cargarMotivosFinalizacion()
{
    ViewBag.motivosFinalizacion = db.SFI_AtributosDbSet.Where
    (x => x.Tipo_Atributo == "MOTIVO FINALIZACION").OrderBy(x =>                 
    x.Descrip_Atributo).Select(x => new SelectListItem
    {
         Text = x.Descrip_Atributo,
         Value = x.ID_Atributo
    }).ToList();
}

Reason_Finalization in the database has the code that should be selected in the dropdown but it does not work. Apparently there are many things that I am doing wrong but it is my first project and I do not know what would be the correct way.

The model is:

public class SFI_Salarios
{
    [Key]                
    [Column(Order = 0)]
    //[ForeignKey("usuario")]        
    public string Win_User_ID { get; set; }

    public string CUIL { get; set; }

    [DisplayFormat(DataFormatString = "{0:N0}", ApplyFormatInEditMode = true)]
    public decimal Salario_Base { get; set; }

    [Key]
    [Column(Order = 3)]  
    [Required(ErrorMessage = "Fecha de Inicio obligatoria")]        
    [DataType(DataType.Date)]
    [DisplayFormat(DataFormatString = "{0:dd-MM-yyyy}", ApplyFormatInEditMode = true)]
    public string Fecha_Inicio { get; set; }

    [DataType(DataType.Date)]
    [DisplayFormat(DataFormatString = "{0:dd-MM-yyyy}", ApplyFormatInEditMode = true)]
    public string Fecha_Fin { get; set; }
    public string Motivo_Finalizacion { get; set; }
    public string Otros_1 { get; set; }

    public virtual SFI_Usuarios usuario { get; set; }


}

View:

@using PagedList;
@using PagedList.Mvc;


@model IPagedList<sfi_1.Models.SFI_Salarios>

@{
    ViewBag.Title = "Salarios";
}

<script type="text/javascript" src="@Url.Content("/Scripts/funcionesJS.js")"></script>


<script>

    $(document).ready(function ()
    {
        cambiarFormatoFechaIndex();
    })
</script>


@using (Html.BeginForm("Index_Deshabilitados", "SFI_Salarios", FormMethod.Get))
{
    IEnumerable<SelectListItem> listaVendedores = (IEnumerable<SelectListItem>)ViewBag.vendedores;
    IEnumerable<SelectListItem> listaMotivos = (IEnumerable<SelectListItem>)ViewBag.motivosFinalizacion;   

<table class="table">
    <tr><th></th></tr>
    <tr>
        <th><h2>SALARIOS HISTORICOS</h2></th>
    </tr>
    <tr>
        <th>
            <div class="row">
                <div class="form-inline">
                    @Html.DropDownList("vendedor", listaVendedores, "Seleccionar Vendedor", htmlAttributes: new { @class = "form-control", @id = "IndexSalarioVendedor" })
                    <button type="submit" class="btn btn-primary"><span>Buscar</span></button>
                    @Html.ActionLink("Nuevo Salario", "Create", null, htmlAttributes: new { @class = "btn btn-primary" })
                    @Html.ActionLink("Limpiar Filtro", "Index", null, htmlAttributes: new { @class = "btn btn-primary" })
                    @Html.ActionLink("Mostrar Habilitados", "Index", null, htmlAttributes: new { @class = "btn btn-primary" })

                </div>
            </div>
        </th>
    </tr>
</table>


<table class="table" id="tablaIndexSalarios">

    <tr>
        <th>ID Usuario</th>
        <th>Nombre Vendedor</th>
        <th>Salario</th>
        <th>Fecha Inicio</th>
        <th>Fecha Fin</th>
        <th>Observaciones</th>
    </tr>

    @foreach (var item in Model)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.Win_User_ID)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.usuario.Nombre)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Salario_Base)
            </td>
            <td id="fechaInicio">
                @Html.DisplayFor(modelItem => item.Fecha_Inicio)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Fecha_Fin)
            </td>
            <td>                                
                @Html.DropDownListFor(modelItem => item.Motivo_Finalizacion, listaMotivos, "", htmlAttributes: new { @class = "form-control", @id = "IndexSalarioVendedor" })
            </td>
            <td>
                @Html.ActionLink("Editar", "Edit", new { winUser = item.Win_User_ID, fecha = item.Fecha_Inicio }, htmlAttributes: new { @class = "btn btn-primary " })
                @Html.ActionLink("Borrar", "Delete", new { winUser = item.Win_User_ID, fecha = item.Fecha_Inicio }, htmlAttributes: new { @class = "btn btn-primary " })
            </td>
        </tr>
    }

</table>
}

@Html.PagedListPager(Model, page => Url.Action("Index", new { page }))

Controller that loads the data:

public ActionResult Index_Deshabilitados(string vendedor, int? page)
    {
        try
        {
            if (HttpContext.Application["codigoPerfilUsuario"].ToString() == null)
            {
                return RedirectToAction("Index", "Home", null);
            }
        }
        catch (Exception)
        {

            return RedirectToAction("Index", "Home", null);
        }

        if (!validacionUsuario("Otros_2"))
        {
            return RedirectToAction("usuarioNoHabilitado");
        }
        cargarListaVendedores();
        cargarMotivosFinalizacion();


        return View(db.SFI_Salarios.Where(x =>
        (string.IsNullOrEmpty(vendedor) ? true : x.Win_User_ID == vendedor))//.OrderBy(x=> x.usuario.Nombre)
        .OrderBy(x => x.usuario.Nombre).ThenBy(x => x.Fecha_Inicio).ThenBy(x => x.Fecha_Fin).ToPagedList(page ?? 1, 20));


    }