The relation between Surah Al-Feel and Surah Quraish is obvious. Allah (swt) destroyed the companion of the elephant to give Quraish safety against fear so that they practice the caravan of winter to Al-Sham and that of summer to Yemen. On the other hand, it is necessary not for a Surah to be revealed immediately after the other one connected with it, but it may be revealed after a time but it had a certain arrangement in the Holy Qur’an. As known, the arrangement of the Surahs in the Holy Qur’an is according to that in the Preserved Tablet.
As for the reasons of the Surahs and verses revelation, this depends on the events. Later, Jibril (puh) arranged them for the Prophet (saws) as in the Preserved Tablet.