Rabbi David Fohrman in his book, “The Passover you almost passed over,” offers an interesting explanation for the ten plagues in Egypt.
Rabbi Fohrman explained that the world at that time was heavily involved in paganism. The Torah tells us that the purpose of the plagues was to make it clear that there was only one true G-d in the world.
The problem with paganism was that their believers attributed powers to specific gods. There was the god of the seas, the gods of the sun, perhaps the god of the animals, etc. They made offerings to these gods and were careful not to anger their respective deities.
Had there been only a few plagues, or one major plague, the pagan worshippers would not have been convinced that it was our G-d, but perhaps, theirs.
However, after ten very different plagues, it would have been difficult to come up with ten different gods. The only conclusion to be made was that it was one G-d, the G-d of Israel, who was showing that He is the only true G-d and all others were false. The ten plagues were a convincing way to make this emphatic statement.