Laravel API: Timestamps (updated_at, created_at) are null

I have an API where the user creates the violation information of a certain driver and when I try to input a data into the table using Postman, the created_at column is NULL when it should not be. What could be the problem?

The code below is the lines of code Controller of when storing the data:

public function store(Request $request)
    {
        $rules=[
            'Driver_ID'=>'nullable',
            'Truck_ID'=>'nullable',
            'Date_happened'=>'nullable',
            'Time_happened'=>'nullable',
            'offense_level'=>'nullable',
            'violation_list'=>'required',
            'status'=>'nullable',
            'ml_violation'=>'nullable',

        ];
        $validator = Validator::make($request->all(), $rules);
        if($validator->fails()){
            return response()->json($validator->errors(),400);
        }

       $data = $request->validate([
            'Driver_ID'=>'nullable',
            'Truck_ID'=>'nullable',
            'Date_happened'=>'nullable',
            'Time_happened'=>'nullable',
            'offense_level'=>'nullable',
            'status'=>'nullable',
            'ml_violation'=>'nullable',
       ]);

    //    $violationsInformation = Violations::create($data);


        $violation_list = json_decode($request->input('violation_list'));

        $final_array = [];

        foreach($violation_list as $key => $value){

            array_push($final_array, [
                // 'id'=>$id,
                'Driver_ID'=>  $request->input('Driver_ID'),
                'Truck_ID'=>  $request->input('Truck_ID'),
                'Date_happened'=> $request->input('Date_happened'),
                'Time_happened'=>  $request->input('Time_happened'),
                'violation_list_id'=> $value->id,
                'offense_level'=>  $request->input('offense_level'),
                'status'=>$request->input('status'),
                'ml_violation'=>$request->input('ml_violation'),
            ]);
        }


        //$quizRecords = Quiz_Records::create($final_array);
        // $violationsInformation = Violations::create($data);
        $violationsInformations = DB::table('violation_information')->insert($final_array); // Query Builder approach

       return response(['message'=>"Violation's Information successfully created",
                             'error'=>false,
                             'error_code'=>200,
                             'line'=>"line".__LINE__."".basename(__LINE__),
                             'violationsInformations'=>$violationsInformations],200,[],JSON_NUMERIC_CHECK);
    }

In database

You should set type of created_at : timestamp or datetime

And Options is (ON UPDATE)

And default is CURRENT_TIMESTAMP

sql :

ALTER TABLE `your_table`
CHANGE `created_at` `created_at` datetime NULL DEFAULT CURRENT_TIMESTAMP;