I had a similar experience. Two months ago I launched my website in 30 new languages on subdomains (in addition to the 10 languages I already had). Google crawl rate on my main English site dropped dramatically when I did this. For me there was no corresponding drop in traffic. I did not to the analysis to see if total crawl volume was up or down. I suspect that it is about the same, maybe a bit higher. Because Googlebot has to spider all this new content, it doesn't have as much time for the content it already knows about.
Interestingly, the crawl rate to another unrelated site of mine on the same server also decreased dramatically at the same time. It could be that Google doesn't want to hit the server itself too hard and that is the limiting factor in the crawl rate.