I know people here rail against parallelism. However, it often seems forgotten that authors like Turtledove are seeking to attract as many readers as possible. It is a challenge for even an averagely well-informed reader to make a jump into reading a book set in a historical period in which all the names are different. It seems instead to be fantasy or science fiction, so a lot of the 'what if?' considerations are lost from reading the book. The parallel characters and indeed events, are an important 'bridge' to bring the ordinary reader over into a different world and have them focus on the differences, which surely are at the heart of alternate history writing, rather than having also to get to grips with the backgrounds and personalities of a whole range of individuals that are new to them.
Please have some more sympathy for authors writing alternate history, because parallelism is essential if they are going to get the kind of numbers of readers which can keep them working as full-time authors.
Also remember that authors are not omnipotent gods with their novels. Anyone who has had their work professionally edited, sought to get an agent or publish in a traditional way, will know how much power editors, agents and publishers have in shaping the 'product' to what they feel will sell best, often moving the book well away from what the author intended. This may be why Turtledove has also self-published with 'Shtetl Days' (2011), though it sits under Tor's umbrella, the author had far more autonomy with that book. That allowed him to address a similar theme but in a way that perhaps hard-core alternate history fans would find more to their taste but would be challenging to Turtledove's wider, usual audience.