Absence of God causes nihilism. But the mere fact of the reality of God does not solve nihilism. God is necessary but not sufficient.
This is indeed why Christianity is necessary. If God was sufficient, there would be no need for Jesus - and Judaism/ Islam would be better (being more simply coherent and not having that distraction).
God is an essential part of the solution to nihilism - God is the primary creator. And creation is love-in-action.
Nihilism is solved (for God as well as for ourselves) by creation - more exactly by our choice in permanently joining creation as eternal and divine (i.e. resurrected) Men. We do this because of love.
The solution to nihilism is participation in loving-creation.
When I state baldly that it is The Solution - more exactly it is the solution for those for whom it is the solution: me for example.
I can understand why loving-creation might not be the solution for someone incapable of love (for example) - such a person might not have a solution to nihilism (e.g. a genuine psychopath).
Or, a person who deeply and permanently disliked all Men and prefers solitude to family (e.g. perhaps a genuine adherent of ascetic negative Buddhism who has no attachment to anything).
What about the past? - when Men had god/s but were not-Christian - and were not nihilistic? The answer relates to the evolution of consciousness. In the past (and still, for some Men in the present) their consciousness is not sufficiently developed that they can be nihilists - a nihilist must be sufficiently self-aware to recognise he is not the universe.
Young children, also, are not nihilists - because children do not distinguish them-selves from the not-self. They are (almost wholly) immersed-in reality.
What of Satan - what does he offer? To those who cannot or do not love; it may be the 'promise' of having consciousness abolished, so as to escape nihilism in just-being - and that state of just-being made pleasurable by using other beings for that pleasure.
So the answers to nihilism (in those sufficiently developed in consciousness to experience nihilism) include to join loving-creation on the one hand; and annihilation of consciousness (and the capacity for nihilism) on the other hand.
To put it simply, God made creation so that there was a purpose and meaning in the midst of chaos (chaos entails nihilism); and creation is an opt-in cure for nihilism for those of us who want it.
Note: The above post is an edited and expanded version of a response to WmJas in a comment thread to an earlier post: https://charltonteaching.blogspot.com/2019/06/the-incoherent-insanity-of-having.html