Laravel filled() method seemingly not working

I am working on a function to update profile details, in my ProfileController.php. I am validating the request, making sure nothing is required, however when I use the filled() function:

        if($request->filled('username')){
            $user->username = $request['username'];
        }
        if($request->filled('email')){
            $user->email = $request['email'];
        }
        if($request->filled('profile_description')){
            $user->profile_description = $request['profile_description'];
        }

This does not work, and the database will only update when all fields have been filled, except for the profile picture:

        if($request->hasFile('file')){
            if ($request['file']->isValid()) {
                $file = $request['file'];
                $destination = 'images/profile_pictures'.'/';
                $ext= $file->getClientOriginalExtension();
                $mainFilename = $user->username;
                $user->pfp_file_extension = $ext;
                // check if user has existing pfp
                if (File::exists($destination, $mainFilename.".".$user->pfp_file_extension)) {
                    File::delete($destination, $mainFilename.".".$user->pfp_file_extension);
                }
                $file->move($destination, $mainFilename.".".$ext);
            }
        }

For some reason hasFile() is working as it allows me to not upload a picture.

I’ve read the Laravel documentation and it states "The field under validation must not be empty when it is present", which does not explain why it is not working. Here is my HTML form input.

<form method="POST" enctype="multipart/form-data">
                @csrf
                <h6 class="heading-small text-muted mb-4">User information</h6>
                <div class="pl-lg-4">
                  <div class="row">
                    <div class="col-lg-6">
                      <div class="form-group focused">
                        <label class="form-control-label">Username</label>
                        <input type="text" id="username" name="username" class="form-control form-control-alternative" placeholder="{{ Auth::user()->username }}">
                      </div>
                    </div>
                    <div class="col-lg-6">
                      <div class="form-group">
                        <label class="form-control-label">Email address</label>
                        <input type="email" id="email" name="email" class="form-control form-control-alternative" placeholder="{{ Auth::user()->email }}">
                      </div>
                    </div>
                    <div class="col-lg-6">
                      <div class="form-group focused">
                        <label class="form-control-label">Profile Picture</label>
                        <input type="file" class="file" name="file" id="file" accept=".png, .jpg, .jpeg">
                      </div>
                  </div>
                  <div class="row">
  
                  </div>
                </div>
                <hr class="my-4">


    
                <!-- Description -->

                <h6 class="heading-small text-muted mb-4">About me</h6>
                <div class="pl-lg-4">
                  <div class="form-group focused">
                    <label>About Me</label>
                    <textarea id="profile_description" name="profile_description" rows="4" class="form-control form-control-alternative" placeholder="{{ Auth::user()->profile_description }}"></textarea>
                  </div>
                </div>
                <div>
                  <button class="btn btn-sm btn-primary" type="submit">Update Profile</button>
                </div>
              </form>

Also, here is the entirety of my ProfileController.php.

<?php

namespace AppHttpControllers;

use IlluminateHttpRequest;
use IlluminateSupportFacadesAuth;
use IlluminateSupportFacadesFile; 


class ProfileController extends Controller
{

    public function index()
    {
        return view('profile');
    }
    
    public function profileUpdate(Request $request){
        //validation rules

        $request->validate([
            'username' =>'min:4|unique:users,username|string|max:255',
            'email'=>'unique:users,email|email:filter|max:255',
            'profile_description'=>'string|max:10000',
            'file'=> 'max:10000'
        ]);
        $user = Auth::user();

        if($request->filled('username')){
            $user->username = $request['username'];
        }
        if($request->filled('email')){
            $user->email = $request['email'];
        }
        if($request->filled('profile_description')){
            $user->profile_description = $request['profile_description'];
        }

        if($request->hasFile('file')){
            if ($request['file']->isValid()) {
                $file = $request['file'];
                $destination = 'images/profile_pictures'.'/';
                $ext= $file->getClientOriginalExtension();
                $mainFilename = $user->username;
                $user->pfp_file_extension = $ext;
                // check if user has existing pfp
                if (File::exists($destination, $mainFilename.".".$user->pfp_file_extension)) {
                    File::delete($destination, $mainFilename.".".$user->pfp_file_extension);
                }
                $file->move($destination, $mainFilename.".".$ext);
            }
        }



        
   
        $user->save();
        return back()->with('message','Profile Updated');
    }

    
}

Thank you in advance.