This is a great question. Let me make three points.
First, Christianity Todayis the most important magazine for evangelical Christians in America. Its influence is strong when it comes to shaping the minds of evangelicals. This is a powerful thing, because in many ways America is still a Christian country. So, when Christianity endorses something or someone, or takes a strong stance against something, many evangelicals take this is as "gospel truth." The influence, therefore, is strong.
Second, for example, one of the hot button issues for evangelical Christians and society is the issue of abortion. So, when Christianity Today respects the thoughts of a Christian thinker like Francis Schaffer, who is outspoken against abortion, then this creates a battle cry among evangelicals against an issue like abortion. We can clearly see this a generation ago, when the battle in this area was strong. We will see this in the future with other cultural issues.
Third, from a sociological point of view, because Christianity Today is so respected among evangelical, what they say creates a feeling of commonsense among evangelicals. This shapes the moral sensibilities of this group, which in turns shapes others.