You were right. After some searching I too came to the same conclusion of decreased tax. After all, other factors contributed simple changes only.Without looking into it since I'm not invested in Intel at all I'm gonna guess it is the new tax law allowing them to repatriate overseas cash at a lower rate. The rules allow companies to do it over time (up to 8 years) so it may impact multiple years. There's also the impact of lower tax rates for profits made in the US.
A company will have previously declared that income, but they may or may not have reserved money for future taxes owed when the money was brought back to the US. If Intel was reserving money at a higher rate than they actually ended up having to pay, the freed up money becomes profit at repatriation time. Some companies were reserving little or nothing against future taxes to juice their income numbers, but Intel was profitable enough they wouldn't have needed to play those games.