1)They thought there was no one left in the World(Ibn Ezra and Kaspi,Rashi and Rashbam)
2)Radak says they thought no one would marry them since they came from the destroyed cities they would be outcasts
3)Seforno has the Most intriguing answer they held themselves to have a great Yichus and there was no one good enough left to Marry.
- They thought there was no one left in the World (ibn Ezra and ibn Kaspi, Rashi and Rashbam)
- Radak says they thought no one would marry them since they came from the destroyed cities they would be outcasts
- Seforno has the most intriguing answer -- they held themselves to have a great Yichus and there was no one good enough left to marry.