Well first of all, the English names of the days of the week aren't actually named after Norse deities, but rather their counterparts in the pantheon of the early English speaking peoples. Woden, Tiw, Thurs, Frigga, and company have their counterparts in Odin, Tyr, Thor, and Frey of the Norse world, but these were not necessarily the same deities. Similar to how the Roman worship of Gods like Jupiter and Mars differed from the Greek worship of Zeus or Ares. The gods were similar and mutually acknowledged, but also different in many of the finer points. Now sadly, very few sources survive that depict the pre-Christian English deities, but there almost certainly different than t

The early iron age deities of the Germanic world were not set in stone. The Norse mythology that we are familiar with today comes from a rather specific time and place, Iceland in the high Middle Ages to be precise, and its relationship to the actual practices of the pre-Christian Norse is...tangential at best. For example, the sagas focus in on deities that are actually rather unattested in the actual arcaheological sources for Medieval Scandinavia. Gods like Odin and figures like Loki are, respectively, uncommon, and non-existent in archaeological evidence. Deities were also popular in different areas of the world and often received different attributes or characteristics as time went on. For example, Tyr was the predominant deity of much of Scandinavia prior to the Viking age, Odin's status as chieftain of the Gods was a much later development (and probably limited to the elite in society), consequently places that bear Tyr's name are very common in places like Denmark, but largely absent from Sweden.

Nor was the pagan etymology of the days of the week a particular problem even after Christianization. Many names for the days of the week across Europe are derived from the names of pagan deities. For example in French, the days of the week are also derived from pagan gods like Jupiter, Venus, and Saturn (One of these survives in English as well, Saturday) as well as the Sun and Moon (another commonality). There is a bit of a complicated history to this, and it related back to a Roman concept, interpretatio Romana which was how the Romans perceived foreign deities. Being a polytheistic religion the Romans were accustomed to encountering numerous different gods and goddesses. The Romans invariably translated them according to their understanding of the divine. So Germanic deities, Gallic deities, Egyptian ones, etc... were all given Roman equivalents. Mercury and Odin for example were often compared, Thor and Hercules, Mars and Tyr, and so on down the line.

These names for the days of the week, each with a pagan counterpart in Romance and the Germanic world, stuck well enough that not even Christianization could dislodge them from the vocabulary, though truthfully there never seems to have been an effort to actually do this either by Christian elites.