Angular *ngFor loop in bootstrap 5 grid columns not right

You're looping over on the container, move the ngFor to your col-md-6:

<div class="container">
    <div class="row">
      <div class="col-md-6" *ngFor="let item of items">

        <div class="card">
            <div class="card-header">
              Heading here
            </div>
            <div class="card-body">
             Body here
            </div>
          </div>

      </div>
    </div>
  </div>