Christianity is an exclusive religion.
This means that Jesus Christ claimed that there is only one way to salvation, and this is through Jesus Christ alone. Every other religion, in the eyes of Christianity, is false religion.
Thus, American Christians who hold to the exclusive claims of Christianity like the fact that Donald Trump is calling other religions false religions.
In a sense, many Christians in America think that those who support religious tolerance are afraid to proclaim the Gospel Truth that Christianity is the only true religion. They feel that such individuals who support religious tolerance are not filled with the Holy Spirit.
When American people see Donald Trump attacking Islam, they feel that Donald Trump is brave and bold in defending Christianity.
That is why so many evangelical Christians have changed their support and now support Donald Trump.
Evangelical Christians do not want a political candidate who will grovel before other religions, such as Islam.