Too many things going on in that game makes it a not particularly good example of any of them, IMO.
You were so much better than the opponent that you could have won that game without chapel, or without Witch, or without Grand Market. That makes it a not particularly useful for demo purposes. The lesson to take away from that game is 'be better in all possible ways'.
Heck, your opponent started with his buys being Workers Village, Warehouse, Chapel, Workers Village (using 5 and passing up a Mountebank!). Of the various things to learn, 'not letting your opponent get all the Grand Markets' is so far down the list; he couldn't have prevented you from doing that if he tried.