Bootstrap grid css loses responsiveness under 1200 pixels wide screens

Question

I have a cshtml site with two bootstrap cards side by side. After I reduce the width of the screen under 1200 px, the cards become wider and lose responsiveness. (There is a file explorer on the left side and the left card slides behind it.)

I have tried

@media (max-width: 1200px) {
  .container {
    width: 100%;
  }
}

I expect the cards to be responsive on smaller screens.