There is a tendency (perhaps depending on where we live), to view ‘pagan’ Mercia as somehow inferior to ‘Christian’ Northumbria due no doubt to Bede the champion of all things Northumbrian. But Mercia, with its centre on the Trent river and its tributaries, became a strong kingdom in its own right covering south Derbyshire, Leicestershire, Nottinghamshire, Staffordshire and northern Warwickshire. In time, from 6-9C, its kings steadily took control of Lindsey, East Anglia, Essex, Kent, Sussex and Wessex, until such time as the latter became the dominant power. The seat of the diocese of Mercia was first Repton, then Lichfield. Christian missionaries were allowed in and gained a foothold till such time as royals and nobles got into the habit (!) of founding monasteries through out the land. This expansion of Mercia was an important step in the creation of ‘England’.
Vikings from Denmark, Norway and southern Sweden, were at first raiders until in 865 they formed a unified command called the Great Heathen Army, or the Great Danish Army to conquer the land. They conquered a whole slice of the country on the northern, central and eastern side and made them subject to the Danelaw
The reason that we have little enough about many saints is that the story of their lives and exploits were swept away. Indeed so thorough was the devastation of the Danes that they more or less wiped the monasteries out.
Or, to put it another way, when the time for restoration came under Alfred the Great no monks could be found to start them up again. They had to be supplied from the continent – and that meant the new style under the Rule of St Benedict as promoted by the Pope.
The irony was that independent kingdom of the Anglo-Saxons under Alfred became the Kingdom of England ruled by the Danes under Canute – who by the mercy of God had then become Christian.