This isn't exactly a dramatic change, the tagline from the article:

The arrival of 2,500 Marines and another 2,500 sailors is keeping the number of American troops in the region at roughly 10,000 more than usual.

That's 'a couple extra ships and some additional flightline mechanics and the associated support staff' numbers. While I'd prefer they were all at home instead of stuck backing up cesspits like Dubai and Doha, this isn't a particularly huge buildup.