Answer by taking a quote from the following article:

Timur was born in Transoxiana near the city of Kesh (modern Shahrisabz, Uzbekistan) some 80 kilometres (50 mi) south of Samarkand, part of what was then the Chagatai Khanate. His father, Taraqai, was a minor noble of the Barlas, a Mongolian tribe that had been turkified in many aspects. According to Gerard Chaliand, Timur was a Muslim, and he saw himself as Genghis Khan's heir. Though not a Borjigid or a descendent of Genghis Khan, he clearly sought to invoke the legacy of Genghis Khan's conquests during his lifetime.

Timur is regarded as a military genius, and as a brilliant tactician with an uncanny ability to work within a highly fluid political structure to win and maintain a loyal following of nomads during his rule in Central Asia. He was also considered extraordinarily intelligent - not only intuitively but also intellectually. In Samarkand and his many travels, Timur, under the guidance of distinguished scholars, was able to learn the Persian, Mongolian, and Turkish languages. (according to Ahmad ibn Arabshah, Timur didn't know Arabic) More importantly, Timur was characterized as an opportunist. Taking advantage of his Turco-Mongolian heritage, Timur frequently used either the Islamic religion or the law and traditions of the Mongol Empire to achieve his military goals or domestic political aims. Timur, mostly considered a barbarian, in fact was a well learned king, and did enjoy the company of scholars --he was tolerant and generous to them against his nature. Once Persian poet Hafez wrote a ghazal whose verse says if this Turk accept his homage:  --For the black mole on his cheekI would give the cities of Samarkand and Bukhara  Timur upbraided him for this verse and said; "By the blows of my well tempered sword I have conquered the greater part of the world to enlarge Samarkand and Bukhara, my capitals and residences; and you pitiful creature would exchange these two cities for a mole". Hafez replied "O Sovereign of the world, it is by the state of similar generosity that I have been reduced, as you see my present state of poverty." It is reported that the King was amazed by the witty answer and the poet departed with magnificent gifts.  Timur used Persian expressions in his conversations often, and his motto was the Persian phrase rasti rusti (rsty rsty, meaning "truth is safety" or "veritas salus").

Was there a reason he was so tolerant?