I think that there has to be a bit more clarity to the question. The question presumes that Islam had a period of diminishment and regeneration. Some would argue that this is not the case and Islam is unique because of it:
The call to fundamentalism, centered on the sharia: this call is as old as Islam itself and yet still new because it has never been fulfilled, It is a tendency that is forever setting the reformer, the censor, and tribunal against the corruption of the times and of sovereigns, against foreign influence, political opportunism, moral laxity, and the forgetting of sacred texts (Olivier 4).
Islam has always been fervently and zealously defended and preserved. If we are examining the state of Islam in the last fifty years, I would say that it has played a large role in world history. The creation of OPEC and the proliferation of oil in the Gulf region has played a large role in how the West, and more recently nations like India and China, interact with Islamic nation. These nations coalesced in the 1970s to create the energy crisis in quadrupling the price of oil, generating large reservoirs of wealth that were used for the establishment of mosques, learning centers, universities and think tanks that spread Islam to more people. Many at the time believed that devout faith in Allah and Islamic principles was the reason why the OPEC nations were able to enjoy the wealth provided by the oil reserves strategically located in this part of the world. Another critical event was the rise of the Ayatollah in Iran, proving that a strict read on Islam can be politically possible. The growth of a fundamentalist Iran played a large role in world history as Iran was a geopolitical and diplomatic prize that was strategically placed in a location that allowed for great access to the region. Negotiating this was another issue, as the Iranian government proved to be a formidable power for Western nations, one that was not going to be bullied over in the desire for consolidating power. I would also say that the recent fears over the growing threat of terrorism and how Islam, or the distortions of it, play into this has had an impact on world history. Over the last half decade, a growing awareness has developed that alienated, economically marginalized, and spiritually disaffected youth are being actively recruited and sought out by organizations who sponsor worldwide terror. Their primary allure is the application of Islam, or a version of it, that speaks to these youth. Western nations are becoming more attune to the need to bring these individuals into the fold as soon as possible. In ignoring the problem, another 26/11, 7/7, 9/11, or Spanish Train bombings could be more likely. However, all of these thoughts are precluded by the need for greater detail on what is meant by "Muslim Resurgence."