Complex sentence: However, in marked contrast to the historical Medieval Europe, Christianity never becomes dominant in the Isles: it is tolerated as one among a bewildering array of religions, and the rulers and people alike prefer it not to become more than that.
Split into simpler sentences: However, in marked contrast to the historical Medieval Europe, Christianity never becomes dominant in these islands. It is tolerated as one among a bewildering array of religions, and the rulers and people alike prefer it not to become more than that.