I'd posit that's because a growing Islamic movement allows power to rapidly shift outside the established political structure. Just like with papistry in Europe

I'd posit that's because a growing Islamic movement allows power to rapidly shift outside the established political structure. Just like with papistry in Europe in the past, if you're using people's faith to manipulate them then someone coming in and 'stealing' those people's adherence means your power is depleted. Islam was arguably designed by Mohammed to cede power from the establishment of his time. Joseph Smith's (Mormonism) very obvious deceptions lead to a new global power structure; Ron Hubbard's (Scientology) even more obvious deceptions are used to target individuals in powerful positions and gain leverage over them. Those who truly believe will always have a negative reaction to religious ideas that challenge their truth; those who use religion to bolster power will be even more against new religious ideas.