How do two gel shampoos turn into water when mixed?

i have mixed a clarifying shampoo with a acidic chelating shampoo, alone they are both thick but if mixed they become thin as water. what causes this ?How do two gel shampoos turn into water when mixed?
my guess is that the shampoos must be polar. like dissolves like so having 2 polar substances together will cause them to dissolve into something ,like you said, 'thin as water'