The promise of a heavenly afterlife can certainly be construed as being motivated by fear of death, and it can also be construed as a threat considering most branches of Christianity menace disbelievers with hell. However, this isn't very satisfying, because the Christian narratives (varying by denomination) have quite a bit more meat to them than just being scared of death and Jebus comes to CTR+Z you unaliving. If it revolved around merely being afraid of death, one would construct a religion that promises universal salvation with no other theological ideas, and while some branches of Christianity do promise universal salvation, most do not, and as far as I'm aware, even the ones that do, have quite a few other theological ideas alongside that one.
Just off the top of my head, Christianity has elaborate scripture on creation, eschatology, ethics, history, and philosophy. There's complex narratives to support all of the above, which I will spare you in this thread. And that's just going by sola scriptura, without getting into things like the traditions of Orthodoxy or the extrabiblical scriptures such as the Gnostic or Mormons, which expound upon a lot of these topics in even greater detail.
Trying to reduce Christianity down to "they're simply afraid of death" just, isn't really correct. Even if you think it's ultimately bullshit.