But where does the gradually increased start from?Would an animal evolve faster in some ways if there was a more dire need to evolve with less risk? Like the trees started getting bigger where they roamed, so their necks grew in response. Why wouldn’t they evolve to eat smaller bushes (when their long necks weren’t a part of their evolution yet.)?

Maybe since they were already accustomed to eating from trees, they evolved to have longer necks. So the stimulus of successfully eating may be coded in their DNA that is passed down. And if tall trees slowly began dying and trees began to shrink to shrubs over millions of years but not slow enough to make them go extinct, would they evolve to have smaller necks? I think so, but because they really began having difficulties eating small things and somewhere in their DNA their evolutionary path changed.

I do agree with you that it was because the ones that had longer necks had a better survivability and bred more to continue the evolution. But what do you think about what I said?