Think of a cheap and flimsy shocks in a car going over a bump at speed, and now think Land Rover, off road quality shocks going over that same bump at speed...
Its shown that a person that has weak lower limb strength ha 6-7 times the chance of injury compared to a person with good lower limb strength when there is a spike in load (Huge et al.)
The same study also showed that fatigue to the lower limbs in runners resulted in a reduction of optimal Quad and Hamstring activation, which affect the ground reaction force on foot strike. This not only impacts the pace of the run, but exposes the athlete to loads that the lower limb can not absorb or handle and may result in injury.
Moral of the story: don't skip leg days. Squats, split squats, RDLs and deadlifts performed with good form, are awesome exercises to get you started.
Enjoy and trust the process.