I am not getting the value of my generated text boxes after loading the DOM

I generate text boxes in js based on a value chosen by a number type input :

function updateChannels(input) 
{
    const container = document.getElementById('description-container');
    const count = parseInt(input.value, 10);

    // Empty the container to reset the descriptions
    container.innerHTML = '';

    // Vérifie que l'entrée est un nombre entre 1 et 4
    if (isNaN(count) || count < 1 || count > 4) 
    {
        input.value = ''; // Reset if the value is invalid
        alert('Please enter a number between 1 and 4.');
        return;
    }

    // Add description fields based on value
    for (let i = 1; i <= count; i++) 
    {
        const label = document.createElement('label');
        label.textContent = `Please describe your channel number ${i}`;

        const textarea = document.createElement('textarea');
        textarea.name = `channel_description_${i}`;
        textarea.id = `channel_description_${i}`;
        textarea.className = 'form-control';
        textarea.placeholder = `Description for channel ${i}`;

        // Add the label and text box to the container
        container.appendChild(label);
        container.appendChild(textarea);
    }
}

So, if I choose 1, a text box is displayed, etc… up to 4.

I retrieve all the data from my form with a $request variable in the route, here is the code :

Route::post('/submit_before', function (Request $request) 
{
    
    // Enregistrement de la manipulation
    $manipulation = Manipulation::create([
        'users_id' => $request->input('user'),
        'machines_id' => 1,
        'manipulation_name' => $request->input('manipulation_name'),
        'system_issue' => $request->input('system_free_issue'),
        'system_qualified' => $request->input('system_qualified'),
        'howmany_injections' => $request->input('channelCount'),
        'column_id' => $request->input('column_description'),
        'guard_column_id' => $request->input('guard_column_description'),
        'type_samples' => $request->input('type_of_samples'),

    ]);

    // Récupérer l'ID de l'enregistrement créé
    $manipulationId = $manipulation->id;
    //récupérer le nombre de description de channels :
    $channelCount = $request->input('channelCount');

    // Boucler pour insérer chaque description de canal
    for ($i = 1; $i <= $channelCount; $i++) {
        // Construire dynamiquement le nom de l'input pour chaque description de canal
        $description = $request->input("channel_description_$i");
    
        // Insérer dans la table channels_descriptions
        ChannelsDescription::create([
            'description' => $description,
            'manipulation_id' => $manipulationId,
            'channel_number' => $i, // Numéro du canal (1, 2, etc.)
        ]);
    }
    


    // Rediriger vers la vue `chrono` après l'enregistrement
    return view('chrono');
})->name('submit_before'); // Déplacement de ->name() avant le point-virgule

The problem is that everything is retrieved except the value of my text boxes which are generated dynamically (the name of textareas begins with channel_description_);

#parameters: array:9 [▼
      "_token" => "0dusC043ovYJMZGShMlsBdioLY3nR8Zyw00zrqAO"
      "user" => "1"
      "manipulation_name" => "eerrere"
      "system_free_issue" => "yes"
      "system_qualified" => "yes"
      "channelCount" => "2"
      "column_description" => "21"
      "guard_column_description" => "17"
      "type_of_samples" => "reeee"

They are NULL.

$description = $request->input("channel_description_$i");

null // routes/web.php:72

If I have two, two rows are inserted into the database, but NULL is put in description.

On the other hand, if the text boxes are present when the form loads, I get their values ​​in the $request variable.

Do you have any idea please? Thanks in advance.