I have no doubt that they may have started with that intent. Many have merely become money machines, with no regard for lost souls, no compassion for its older members, and no message of Redemption or Salvation. It is just a "seeker friendly" megachurch that makes tons of money for someone, and it doesn't appear to be for God's glory, but a man's.
A Mega-Church is generally a cult of personality revolving around the preacher.
If it was not, the congregants and Church would do the normal thing and the congregation would divide by creating daughter Churches to keep the size manageable. After all, if it is the message that is important, than the messanger is not important and there should be nothing holding one back from calving off new Churches.