The answer is a partial yes. Historians now think that the "Islamic conquests" actually began as a loose confederation of opportunists exploited a weak moment in the histories of the Byzantine and Persian Empires. While there was undoubtedly a Muslim core to this confederation, a number of groups joined the movement for their own purposes, perhaps not even realizing that religious change was in the air. This may have included restive locals who wanted to throw off imperial taxation for distant wars, Christians who followed one of the many creeds that Constantinople was trying to suppress, or anyone who felt marginalized in the Zoroastrian high culture of the Persian Empire. It also included some baser raiders who saw an excuse for easy plunder.

So what drove the Islamic conquests? An upper echelon of war leaders embraced Islam, and as their areas of operations diverged, it became the definitive tie that joined them as a community. But this community also depended on expansion. Its leaders had previously been nomads, and from their perspective, their power, prestige, and wealth all depended on successful military conquests. Coalitions of nomads from Arabia and Central Asia periodically gathered and washed against the Byzantine and Persian Empires, but this time the empires were weak and Islamic piety joined the leaders into a community that wouldn't disintegrate on impact. So the coalition leaders held things together and despite all odds conquered territories from Morocco to the Oxus.

These were not, then, conquests about spreading religion. A religious community certainly spread with the conquests, but these Islamic leaders could also accommodate people of other religions, and especially people of Jewish or Christian faith. And people of other religions might join the conquests if they were at all dissatisfied with the status quo—and there was much to be dissatisfied about with the Persian and Byzantine Empires enforcing or at least privileging their own particular brands of religion and embroiling the Middle East in seemingly endless war.

It was only after the conquests were complete and people reflected on events that they simplified their stories and started to characterize the conquests uniformly as a holy war. (Jihad meant many things, even in the Quran, and it does not seem to have been the dominant rhetoric used in the 600s.) Islam became a prestigious religion and many people converted for any number of reasons, and if they or their ancestors had participated in the conquests, they began to describe this participation as a pious endeavor. The less respectable participants were gradually forgotten, and the most villainous were sometimes recast as heretics or apostates. By the time al-Tabari wrote his monumental history in the late 800s, these revised stories were well entrenched, and only the work of a few brilliant scholars has helped us piece some of the original stories back together.

I'd strongly recommend looking at Robert Hoyland's In God's Path (2015) as the most daring and compelling interpretation of the Islamic conquests. Hugh Kennedy's Great Arab Conquests (2007) is another brilliant exposition of the evidence and gets into the nuts and bolts of conquest with remarkable clarity.