Routes com name não corresponde

Arquivo web.php da laravel

<?php

use App\Http\Controllers\SeriesController;
use Illuminate\Routing\Route as RoutingRoute;
use Illuminate\Support\Facades\Route;

/*
|--------------------------------------------------------------------------
| Web Routes
|--------------------------------------------------------------------------
|
| Here is where you can register web routes for your application. These
| routes are loaded by the RouteServiceProvider within a group which
| contains the "web" middleware group. Now create something great!
|
*/
Route::get('/', function () {
    return view('welcome');
});

Route::get('/series', 'SeriesController@index')->name('listar_cursos');

Route::get('/series/adicionar', 'SeriesController@create')->name(
    'form_criar_serie'
);

Route::post('/series/adicionar', 'SeriesController@store');

Route::delete('/series/{id}', 'SeriesController@destroy');

Arquivo index.blade da laravel

@extends('layout')

@section('header')
Minhas Series Favoritas
@endsection

@section('body')

@if(!empty($mensagem))
<div class="alert alert-success">
    {{$mensagem}}
</div>
@endif

<a class="btn btn-primary mb-2" href="{{ route('form_criar_serie') }}">Adicionar</a>

<ul class="list-group ">
    @foreach ($series as $serie)
    <li class="list-group-item d-flex justify-content-between align-items-center">
        {{$serie->nome}}
        <form action="/series/{{$serie->id}}" method="post"
            onsubmit="return confirm('Tem certeza que deseja remover{{addslashes ($serie->nome)}} ?')">
            @csrf
            @method('DELETE')
            <button class="btn btn-danger btn-sm">
                <i class="far fa-trash-alt"></i>
            </button>
        </form>
    </li>
    @endforeach
</ul>
@endsection

todo o codigo está rodando normal, porém quando troco o nome da route como o instrutor fez, dá erro

Route::get('/series/criar', 'SeriesController@create')->name(
    'form_criar_serie'
);

aponta pra este erro

Symfony\Component\HttpKernel\Exception\MethodNotAllowedHttpException
The POST method is not supported for this route. Supported methods: GET, HEAD, DELETE.

tendo que voltar para como estava para funcionar novamente