I think a major motivating factor for some people is that they want their children and grandchildren to have a better life. Money might be a part of this, but I think John Adams expressed it best:
I must study politics and war, that our sons may have liberty to study
mathematics and philosophy. Our sons ought to study mathematics and
philosophy, geography, natural history and naval architecture,
navigation, commerce and agriculture in order to give their children
a right to study painting, poetry, music, architecture, statuary,
tapestry and porcelain."
Of course, plain, old fashioned greed and hubris can fuel many a soul.