In the photos on the left and the right are examples of how the typical door frame looks after a door has been kicked in.
In the example on the left, you can clearly see the space between the door frame trim and the 2x4 wall stud. That door trim is the only thing that was keeping that door locked. When it broke, that's what allowed the door to open.
In the example on the right, you can see how much of the door frame actually split apart when the door was kicked-in. This is WHY you must have a LONG (48" or more), STRONG (heavy gauge steel with 3" screws) strike plate on every exterior door.