There is no objection to the Right Side of the Row being longer than the Left
Question :
The Iqamah was called for the 'Isha' prayer and the right side of the row was filled, while there were only a few persons on the left side, so we said: "Make the row even on the left." But one of the worshippers said: "The right is better." However, one of the worshippers corrected him with the Hadith:
"Whoever filled the left side of the rows will have two rewards.
Please deliver a verdict for us regarding which is the correct view in this matter.
Answer:
Evidence has been authentically reported from the Prophet to show that the right side of every row is better than the left, and it is not lawful to say to the people:
"Make the row even."
And there is no objection to the right side being longer, if it be due to the desire to obtain (Allah's) Favor.
As for what one of those present said, regarding the Hadith:
"Whoever filled the left side of the rows will have two rewards.»
I do not know any basis for it.
It seems likely that it is a fabrication invented by some lazy people who do not take care to pray on the right side of the row, or do not compete with others to get to it. And Allah is the One Who guides to the Straight Path.
Source:
Ibn Baz
Fatawa Islamiyah, Vol. 2 Pages 336-337