The biggest influence was companies trying to increase their profit margins. Although there are many people who really do have altruistic purposes, there is a lot of money spent to make crops grow faster, be more resistant to bugs, and look and taste better.
Some large factors have been crop resilience, hardiness, crop yield and needed increase in food supply. It is thought that many peoples struck by draught and famine, by wars and dislocation might benefit from genetically modified corn seed. The irony is that at least some of the nations housing these people have turned away, have rejected, shipments of GM corn as being unsafe and posing too great a danger of health problems: they protest being the testing ground for the new field of GM foods.
Clearly, one of the major things that has affected this development is the development of people's ability to sequence the genomes of different kinds of plants. As this has become easier and cheaper, more GM plants can be produced.
A second factor is the demand for food. There is a desire to increase agricultural productivity in a way similar to what was accomplished during the "Green Revolution." One way to do this is through GM plants.
I would want to argue that one of the most significant factors that has hindered the development of Genetic Modification in the food industry has been a combination of religious protests and the press. I have included an interesting link below to religious views on GM foods which you might find useful, but clearly one of the major arguments against the use of GM technology has been and will continue to be the way that it represents man "playing God" in a Frankenstein fashion. This of course has been picked up by the press who have printed big headlines inciting terror about "Frankenstein Foods" and their incorporation into the food chain of humans. Clearly, the impact that the media has had on the development of GM technology has not been beneficial, as it has helped to stoke the fears of people rather than help to explain GM technology and to give a realistic account of what the issues are concerning this valuable scientific breakthrough.