Hazrat Mahdi (as) will appear when people are least amicable and most at conflict with one another
Mufazzal Ibn Omar says: Imam Abu Abdullah Jaffar Sadiq said: ...And HE [HAZRAT MAHDI (AS)] WILL APPEAR WHEN PEOPLE ARE MOST EVILLY DISPOSED TO ONE ANOTHER.
(Sheikh Muhammad bin Ibrahim Nomani, al-Ghaybah al-Nomani, p. 187)