Few parts, minimal friction contact and straight leverage lines:
When the trigger is pulled, the trigger bow pushes straight back into the sear.
The sear then pivots on its pin. The sear has a limited surface area contacting the hammer, usually only 0.020 inches of hammer hook. That is not a lot of drag. Parts don't have to flex or strain as much as other designs, both flexing and staining add to trigger weight and take away from a crisp pull.
Other designs often have the trigger dealing with things other than tripping the sear and releasing the hammer. For example, the Browning hi Power also has a magazine disconnect that must be overridden by the trigger to trip the sear. That adds to trigger pull weight and adds creep to the trigger pull.
The original 1911 design is mostly easy to work on and improve further from the factory, polishing parts, changing spring tensions, reducing sear/hammer contact area, if necessary.