On Deepawali, alongwith mother Goddess Laxmi Lord Ganesh is worshiped, whereas according to Indian religion and culture Lord Vishnu ought to have been worshiped with Goddess Laxmi. Why so?
Deepawali is a festival of wealth and Laxmiji is a goddess of wealth. But without wisdom wealth is useless. Therefore to acquire wealth and wisdom, Laxmiji and Ganeshji are worshiped.
Ganesha is famous as 'Siddhidayak'. It is very important to worship Ganeshji to make life happy and without obstacles and peaceful.
According to Linga Purana Lord Shiva blessed his son “Oh, obstacle savior, you being the master of obstacles, will be respected and worshiped in all the three worlds. Those who in order to acquire fruits, worship other deities they have to worship you first, then only their prayer would be completed otherwise they will have to face obstacles.”
This way Ganesh became famous as Ganapati, Ganeshwar, Vighneshwar and since than the rule to worship him first came into practice.
Laxmiji can be stabilized through wisdom only. there are many tales about Laxmiji being worshiped with Ganeshji. According to one such tale, a hermit made Goddess Laxmi happy through hard penance and expressed his desire to live up prosperous life. Goddess Laxmi granted him wish and disappeared. Now the hermit went straight to the court and to the king and with a jerk made his crown to fall on the ground. Seeing this the king became red with anger, but suddenly he saw a scorpion coming out of the crown. Seeing this, the king's heart filled with respect and he requested the hermit to be his minister. The hermit wanted this only. He accepted the offer. With the advice of the hermit the work in the palace went smoothly.
Similarly, one day the hermit asked every one in the court to go out. Believing the hermit, all with king left the court and went straight to the ground. Suddenly the walls of the court raged to the ground. This incident stamped faith in the hermit in such a way that every thing was done as he desired. This made the hermit proud.
In the palace, a statue of lord Ganesha was installed. The proud hermit ordered to remove the statue from there, because according to him, the statue was spoiling the beauty of Royal palace. The next day the hermit asked the king to put off his attire as it contained snake. The king had staunch faith in hermit, There fove without caring about courtiers the king put off his attire. There was no snake in it. The king raged with anger and ordered him to be imprisoned
Having spent some days in the prison the proud of the hermit vanished. He again started worshiping Goddess Laxmi. In the dream Laxmiji appeared and told him that his condition deteriorated because he disrespected Ganeshji. Ganeshji is a God of wisdom. He made him angry and spoiled his own wisdom. Repenting, the hermit sought pardon from Ganeshji. Next day the king himself reached there and set him free. He reinstated him as minister. The hermit got the Ganesha statue installed at the same place and started worshiping him with Goddess Laxmiji so that wealth and wisdom could stay together. Since then the Lord Ganesh and Goddess Laxmi are worshiped together on Deepawali.