How to fix Laravel Excel Reader memory leak?

I'm using Laravel Excel "maatwebsite/excel": "^3.1", to import just 400 records with 10 fields. The process of just reading these records needs around 2GB of RAM (just to read data into a collection) reading them in chunks 20 rows per once (I tried increasing chunk size to 50 and it consumed more RAM)

try {
     $collection = Excel::toCollection(
         new UsersImport(
             $entity,
             $user,
             $unique_fields,
             $update_duplicates,
             new JobHistory,
             $this->userTypeRepository,
         ),
         storage_path().'/uploads/' . $usersFileName
     );
   } catch (\Throwable $th) {
      throw new Exception($th);
}

UsersImport.php

class UsersImport implements ToCollection, WithHeadingRow, WithChunkReading, ShouldQueue, WithEvents
{
private $entity, $user, $updateDuplicates, $uniqueFields, $jobHistory, $userTypeRepository;
use RemembersChunkOffset;

public function __construct(Entity $entity, User $user, array $uniqueFields, string $updateDuplicates, JobHistory $jobHistory, UserTypeRepository $userTypeRepository)
{
    $this->entity = $entity;
    $this->user = $user;
    $this->updateDuplicates = $updateDuplicates;
    $this->uniqueFields = $uniqueFields;
    $this->jobHistory = $jobHistory;
    $this->userTypeRepository = $userTypeRepository;
}

public function collection(Collection $rows) {

    /* foreach ($rows as $row) {
        $data = $row->toArray();
        array_walk($data, array($this, 'parseData'));
    } */
}

public function chunkSize(): int
{
    return 20;
}

public function registerEvents(): array
{
    return [];
}

public function headingRow(): int
{
    return 15;
}

}

Why is this happening and how to make it consume less RAM? If I try to import 800 users I'll need 4GB RAM to make it work!!