Unfamiliar wiring on what looks like a single pole switch
I believe they were using the switch to pigtail together the two looped wires and the top back-stabbed wire. The top screw and top backstab are the same terminal of the switch (the other screw and backstab are the other switch terminal). This is probably the hot coming from the source (breaker panel) and being distributed to two other switches.

You can proceed as follows:


Disconnect the looped wire and the top backstabed wire.
Cut the loop to produce two separate wires.
Connect together these three wires, together with either the line wire to the new switch or a short piece of wire (pigtail) to go to the new switch. Be sure to use a proper sized wirenut.
Connect the bottom back stabbed wire to the load terminal of the new switch.


One caution: between adding another wirenut (or two if the switch has its own load wire that must be wirenutted to the load wire) and the size of the new switch, you may well exceed the fill limit of the box. In this case, you'll need to actually remove the box and replace it with a deeper box (not an easy job).