That was done so that Buddhists could later be referred to the Bible and what Jesus would show people. What is more, since Jesus is to return and complete what he was doing, Buddhists are referred to what he said in the past and to what he will say when he returns.
Most Buddhists do not know that the Buddha prophesied Jesus, or that the Buddha believed in God, heaven, hell, sin and the devil. The way to show them is to get the texts of what the Buddha said and politely and respectfully ask them to consider what he said.
You can find specific Buddhist reference points in the following book.
Jesus & Buddha, the Parallel Sayings, ISBN 978-1-84483-770-0
To assist in understanding why the references in that book are directly relevant the following information is added.
For an introduction to this subject see