Laravel validation overwriting my values?

I have a Laravel 5.8 (also tested with Laravel 6.1.0) job that periodically downloads a file from the NOAA Spacer Weather Prediction Centre. As part of the job, I want to validate some of the attributes before inserting them into the database and fail the job if things aren't right.

The SWPC file is a JSON file that contains an array of objects that looks like this:

  [{
    time_tag: "2019-10-02T13:39:00",
    bt: 4.45,
    bz_gsm: 0.09,
    // (there are lots of other, irrelevant fields here)
  }, {
    // (more of the same data here, repeated dozens of times)
  }]

The main part of my job looks like this:

  $request = $guzzle->request('GET', 'https://services.swpc.noaa.gov/json/rtsw/rtsw_mag_1m.json');
  $imf = collect(json_decode($request->getBody()->__toString()));

  Validator::make($imf->all(), [
    '*.time_tag' => 'required|date', // Must be a valid date
    '*.bt' => 'required', // Bt must be present
    '*.bz_gsm' => 'required', // Bz must be present
  ])->validate();

  dd($imf->first());

According to the documentation, calling validate() on a manually created Validator should act the same as if you validated a request object (that is: "If validation fails, the user will automatically be redirected or, in the case of an AJAX request, a JSON response will be returned")

However with the above code, validation passes, but the time_tag, bt and bz_gsm fields are null. If I remove the time_tag validation rule, time_tag is no longer null (but bt and bz_gsm are null). Same with the bt and bz_gsm fields. Basically any field that gets validated, is nulled.

If I change my validation code to this:

  $validator = Validator::make($imf->all(), [
    '*.time_tag' => 'required|date', 
    '*.bt' => 'required|file', // Bt is not an uploaded file! Validation should fail.
    '*.bz_gsm' => 'required',
  ]);

  dd($validator->fails());

Then fails is false (i.e., validation passes). If I dd($imf->first()), then once again time_tag, bt and bz_gsm are null, while every other element in $imf is the original value.

As far as I'm aware, my matches are correct, because dd($imf->all()) before, gives a lot of output that looks like this:

array:2031 [
  0 => {#922
    +"time_tag": "2019-10-02T23:55:00"
    +"active": true
    +"source": "ACE"
    +"range": null
    +"scale": null
    +"sensitivity": null
    +"manual_mode": false
    +"sample_size": 60
    +"bt": 3.48
    +"bx_gse": -3.13
    +"by_gse": 0.58
    +"bz_gse": 1.4
    +"theta_gse": 23.73
    +"phi_gse": 169.57
    +"bx_gsm": -3.13
    +"by_gsm": 0.9
    +"bz_gsm": 1.23
    +"theta_gsm": 20.65
    +"phi_gsm": 164.0
    +"max_telemetry_flag": 0
    +"max_data_flag": 0
    +"overall_quality": 0
  }
// ... a few thousand more lines of output here

while dd($imf->all()) after validation gives me:

array:2032 [
  0 => {#922
    +"time_tag": null
    +"active": true
    +"source": "ACE"
    +"range": null
    +"scale": null
    +"sensitivity": null
    +"manual_mode": false
    +"sample_size": 60
    +"bt": null
    +"bx_gse": -3.16
    +"by_gse": 0.94
    +"bz_gse": 1.2
    +"theta_gse": 20.01
    +"phi_gse": 163.43
    +"bx_gsm": -3.15
    +"by_gsm": 1.2
    +"bz_gsm": null
    +"theta_gsm": 15.69
    +"phi_gsm": 159.09
    +"max_telemetry_flag": 0
    +"max_data_flag": 0
    +"overall_quality": 0
  }
// ... a few thousand more lines of output here

So it's finding the keys it needs, and is just overwriting those while leaving the rest of the info.

Is there some hidden trick to validating arrays of data, or validating data in a Laravel job?

from Laravel validation overwriting my values?