The natural curves of the spine can be unnecessarily increased by over-tight muscles.
For the lower back, hip flexors play a major role in our spine anatomy.
Here is a way to test out if an increased lordosis is due to tight muscles: compare the ability to perform a posterior pelvic tilt in 2 positions.
Start in standing position, with extended legs. TIlt your pelvis backward, and feel how difficult it is to re-create a neutral spine.
Then slightly bend the knees. Bending the knees involves hip flexion. Then tilt your pelvis backward. If this feels easier to perform compared to extended legs, then muscle tightness is a major reason for the lordosis.
Stretching and relaxing the psoas, quadriceps and/or quadratus lumborum can help to correct this.