The Mughals did not follow any law of succession like the law of primogeniture. Consequently, each time a ruler died, a war of succession between the brothers for the throne started. This weakened the Mughal Empire, especially after Aurangzeb. It is generally believed by the historians that one of the major causes of the decline of the Mughal empire was the policy of conflict followed by Aurangzeb with the Rajput’s.
The 16th amendment in 1913 permits Congress to lay and collect taxes on incomes, from whatever source derived, without apportioning it among the states or basing it on the US Census. Ratification was completed on February 3, 1913. Before that customs duties and excise taxes were the primary sources of federal revenue. Answer: The ratification of the 16th amendment.
Details? I'm not sure how to answer, without any real information.
On a "Wing-it" situation. I'd say Europe was poor country-wise.
