I will throw a hat in on this one.
The Bible college ministry started many centuries ago as a way to prepare ministers for ministering the Word of God to the common people. I really don't believe the motive among any group has ever changed from the original intent. As different doctrines, philosophies and methods have permeated old schools of the Bible, new schools have been formed. The modern Fundamentalists came out of many denominations in the 1920's to stand against modernism. It was during this time, I believe after the Niagara Bible Conference, that the determination to start new Bible colleges was decided upon by the leaders of the Fundamentalist movement. When Lee Roberson was voted out of the SBC, he began his own Bible college to train people for ministry. He wanted an academic institution to prepare ministers for ministering the Word of God to the common people.
I believe an evolutionary step took place when Jack Hyles springboarded into the national spotlight with the "World's Largest Sunday School." People wanted to learn HOW the work was done, and thus was the purpose of HAC - training people HOW to get the Gospel to people and people to the Gospel. Following this step, others have had differing ideas about the HOW of ministry, and, so, many different Bible schools have sprung up.
The notion that the IFB college is started for financial gain is laughable. If you have even tried to run a local Christian school, you might begin to understand. Do most of these IFB pastors with a Bible college have a pride problem? Yes. But, then again, so do each of us. After all, we are on here voicing our opinion as if it matters.

I have recognized the apparent need among IFB pastors to start a Bible college, which doesn't need to exist.
Recently, I had an IFB pastor ask me to help him start a Bible Institute at his church. I declined the job offer. He is one of the best friends I have and a good man who has a real heart to help people see God's grace. However, I think training people to disciple people and understand the Bible ought to be the purpose of every church for every member. If we need to change what church looks like on some service times, so be it. I personally don't see the need to have people who have a greater desire to learn and lead pay extra money to have the church perform the duty of a church. If one desires to spend some years of his life to study the Scripture, let him go to such a place that is set aside for that purpose while fulfilling his responsibility to disciple others in a local church.
In short, the Bible college is not a fad. To make such a claim shows a great deal of misunderstanding about church history. Maybe I have helped you see why so many of the small Bible colleges have jumped up.