Soaking lentils increase the mineral absorption rate of the body. An enzyme called phytase is activated when you soak the dal for some time. Phytase helps in breaking down phytic acid and helps in binding calcium, iron and zinc. This makes the absorption process much easier.
Soaking also activates a compound called amylase that breaks down complex starch in lentils and makes them easier to digest.
The soaking process also removes the gas-causing compounds from the lentils. Most legumes contain complex oligosaccharides, which is a type of complex sugar responsible for bloating and gas. Post-soaking this complex sugar content is significantly reduced which further saves you from gaseous troubles.