I have not seen that particular show on the History channel, but I already know what their motivation is for doing a show on the Bible: they want to put out an interesting story that will attract the most viewers, which helps them to make as much money as possible. The History channel is basically all about "selling entertainment" under the disguise of "learning while you watch TV."
They are probably more concerned with telling a good "story" than they are concerned with accuracy and respect to the subject matter they are dealing with. In fact, they like a little bit of "controversy." Anything to get people talking about their show, get people emotionally invested in one side of an argument or another. Telling Christians that their religion is mostly based on "mythology" and things that are not real - that's a perfect way for them to get a lot of people upset and talking about their show.
Don't believe everything you hear on TV. They will claim to be "experts" on everything they talk about - but there are a lot of "experts" out there, with a lot of different opinions on things, and they don't all agree with the same point of view.
The best thing to do is to study an issue for yourself, get information from several different perspectives, and then use your own mind and good sense to come up with your own ideas and beliefs about it. Only you can decide what something means to you. You can choose to base your ideas and beliefs on what other people tell you, you can listen to your parents, your friends, and your teachers - but you can also study things for yourself, and figure out what makes the most sense to you.