Light levels cause your pupil to constrict or relax. When your pupil opens up, the natural spherical aberration of the eye causes “focus shift”, meaning for the same shape of your eye and lens, the optimal focus point moves closer to you (in other words you get slightly more myopic in dim light). Correct prescription with a fully dilated pupil can be 0.75 diopters stronger than with a daylight constricted pupil, though at dusk it’s usually more like 0.25 diopters.
Also the eye focuses blue light more than red, so in evening light the ambient light is bluer, meaning that you are more myopic in dusk light due to the bluer light in the environment. This effect is why blue lights can appear out of focus when red lights aren’t, at the edge of blur.
Finally, the wider your pupil is, the narrower the “depth of field” that you see in focus. With a small pupil (such as daylight), you have a large area in front of and behind the focus plane that looks also in focus. This is called “depth of field”. When your pupil is wide open, that depth shrinks. This is important because if you can’t focus squarely on something, but come up short, it can look sharp still with a constricted pupil (daylight), but fuzzy with a wide open pupil (dusk).
All of this conspires to make your eyesight “worse” in low light situations (compared to bright daylight).
This is also why optometrists test in a dark room, they want to be sure you see sharp when driving at dusk (liability issues). This results in over correction by sometimes a half diopter during daylight, which of course, helps the myopia progression.
So it’s not light levels or lux that matters, but the optics of your eye and its pupil that matters.