Vishnu and Laxmi symbolize the pure awareness and divine creation coming to manifestation. They preserve the divine creation of Sarasvati and Brahma which come from the awareness and pure love of Shiva and Shakti.
In some images Vishnu and Laxmi are resting on Ananda, the great cosmic serpent which represents Kundalini Shakti awakened in its pure blissful state of divine love.
One can also see Lord Buddha, an avatar of Vishnu also depicted sitting with Ananda.
When a person is in a divine state, the universe supports them completely.
Thus the holy Hindu holy trinity is explained as it is.