I think the number of people who read the books is quite small so they kind of had to pander to an audience that hadn't. I kind of enjoyed it but it is a bit...strange.
Asimov is a horrible writer. The books are just bad (with the exception of the first one https://news.ycombinator.com/item?id=39555390). And if you take the series as whole, what they did in the show is really good. Imagine springing the Mule or R.Daneel Olivaw out of nowhere like the books do?