If you regard Galilean relativity as a law of nature then Einstein's 2nd postulate confirms his 1st postulate and vice versa since SR as strange initially this may sound, is consistent with Galilean relativity and actually depends on Galilean relativity.
Even today this is by many not fully understood and cause for misinterpretations and misunderstanding thus non-intuitive. However, this is because this 2nd postulate comes with a condition that is little know or made clear. As soon this condition described herein is understood everything becomes clear in Einstein's Special Relativity (SR) concerning this 2nd postulate.
The illustration below of Fig. 1 explains to what Einstein's 2nd postulate that speed of light being absolute and not depending of the velocity and speed of the observer (receiver) really refers to, and which is IMHO the main root of confusion and difficulty most people have to intuitively understand what Einstein is actually saying?:
Base Graphics Credits: Steffen Kühn
In the first case where the EM wave did not reach yet the receiver (i.e. Broadcast station just transmitted its first wave transmission) propagation times tA and tB from the station to the receiver are different and are depending on the velocity and speed v of the receiver therefore subject of Galilean relativity.
In the second illustration the observer (receiver) has been already encompassed by the transmitted EM wave from the station. This is the case which Einstein SR refers to! The observer (receiver) is already inside the transmitted EM wave and fully surrounded by it. Therefore, tB=tA and independent the speed v of the receiver as long as the receiver is engulfed by the wave. The receiver (observer) is now subject of Einstein's Special Relativity (SR) and not Galilean relativity.
The speed v only generates a frequency Doppler shift of the received frequency of the EM waves but does not affect the propagation speed of the received waves which is always fixed at speed c in a vacuum.
That's it. Nothing really non-intuitive.
That is the key point for understanding Einstein's absolute c speed of light postulate, independent by the velocity of the observer. Einstein assumes that when you see the light on the train coming towards you, since you see the light that means it already has reached you and you are already inside it and engulfed by it.
An observer located within the wavelength of wave does not experience different propagation delays with his motion inside it therefore perceives the wave at constant velocity c in a vaccum independend the observer's relative motion.
So, all laws of nature hold and are the same independent of inertial frame in Einstein's SR even including Galilean relativity. This is the beauty of Einstein's theory.