Note, depends on how much he worked out before hand. If someone was working out who did it casually, then gets serious into heavy weight lifting will see dramatic changes. The size the body can grow in a short time is astounding. Look at football players in college. The change from year one to year two is always huge. In high school they have little knowledge. At Ohio State they have one guy who is dedicated to training and building football player's bodies the right way. You see those guys go from pretty good shape (Tiger pre 2009), to being big linebackers and running backs. It is possible, if you are dedicated enough. Any body who looks up muscle gain naturally finds that a person can easily put on 15-20 lbs of muscle in one year, and that drastically drops yearly till you can only get small gains from year to year due to your body's own limit.
So before you start spouting about how "OMG HE GOT HUGE". It is very much possible depending on how work out routine before and after that he could have gotten that big. Also there are some other supplements out there that are not steroids that promote muscle growth as well.
Also there is very little difference between the images.
In the 2009 photo, he is looking up, which extends the neck forward, which makes it look like his neck is huge. His arms are not much bigger than in 2008. 2008 looks a lot like 2007.
This is an image from 2006, I don't see anything you are saying. No man boobs
Here is another one. Look at the arms, not scrawny at all. Not as big as 2008 or 2009, but not drastic change.
You seem to find a nice convenient image where his shirt clearly makes it look like he is scrawnier than he is.