Are christians ignoring the true Sabbath ,just to be different to jews?

No. They're just doing what they're told without questioning it (big surprise). If they did bother to question it, they'd realize that the only reason the church tells them to honor Sunday as the sabbath is because pre-Christian Roman Pagans used that day to honor the sun god and thought it would be easier to keep the holy day the same when they converted to Christianity.