Can anyone knowledgeable correct / confirm my understanding of why the Lidar technique works?

The Lidar is able to penetrate (or just get in between) gaps in foliage which otherwise obscure or smooth out the features on the ground / dirt-level. So then by taking the lowest ground surface height reached in a certain patch of ground scanned (like sq. ft) you're able to "see" the actual ground?

If so, why didn't radar work previously? Too long wavelength? Or that's like a continuous wave / average scan versus a point-by-point scan?

Thanks!