Why did the Germanics believe into Ragnarök? In Christian mythology, the revelation is basically there to fear the people from going against the Christian way and otherwise ending up in hell. But in Germanic mythology, I thought the idea of ascending to Valhalla goes back to the Viking Age because the Vikings wanted something to rival the Christian heaven. Before that there was only Hel, so you getting to the death world after death was considered as inevitable and you basically just prayed to not have bad luck while still living, for example by not being hunted by Wiedergänger, so what was the point of Ragnarök originally?
There is a common misconception that Ragnarok is the full end. But in all truth, Ragnarok is only the end of the gods or Twilight of the gods. And not even all of them. Mainly Tyr, Odin, Loki, Freyr, Heimdall, Thor, and most the gods on Asgard if not all. Mainly noted survivors will be 2 humans and Baldur, Magdi and Modi (sons of Thor) Vili Vey, many goddesses, and a few others. But most will die and the world will come out from the water and fire covered in lush green plant life. And Asgard and Midgard will be made anew from the survivors.
There is some controversy in Norse studies about whether the idea of Ragnarok originates in paganism or if it was the result of Christian influence on the Nords at that time. There is a good argument to be made that it goes back to Indo-European myth since the idea is found in Persian (Zoroastrian) myth well before the Christian Era (Frashokereti). Hinduism also has the Kali Yuga. Also related are the Greek ideas about the Ages of Man. The underlying idea may be that large periods of time (ages) follow the same cyclical pattern as day and night and summer and winter. Thus, the Fimbulwinter of Ragnarok was followed by the Spring of world renewal; or the dark night where the wolf devours the sun is followed by the new day where the daughter of the sun takes her mother's place.
As for the issue of Valhalla versus Hel, I think the idea of a paradise for the righteous dead is too widespread in Indo-European cultures to be the result of Christian influence. The Greeks had the Elysian Fields. The Celts had Tír na nÓg (Avalon). The Baltic peoples had Dausos. The Vedic Hindus had Svarga... Rather than Christianity influencing Indo-Europeans, it seems more likely that early Jewish Christians were influenced by Hellenistic Greeks since the Middle Eastern Jewish tradition only had the idea of 'Sheol', which was like Hel and Hades, before Christianity.