Bulbing is a great example of the kind of thinking needed to move-up in difficulty levels.
On lower levels, it's sufficient to develop your empire 'optimally' eg., working improved tiles, picking the right buildings for each city, building wonders that are A-good and B-good for your land/civilization. Essentially: finding synergy and making use of it. You then get your empire set-up, wait until you out-pace the AI, then win the victory of your choice.
On higher levels, all the synergy and optimization in the game isn't enough to get you ahead if you don't find short-term opportunities and exploit them. This can mean many things:
- getting a monopoly tech and trading it around for many times its beaker value
- getting a military advantage and leveraging it for more land, or a vassal
- getting a strategic advantage and leveraging it for more land or tech (I would put settling islands with galleons and winning the Music, Lib, Physics, Communism races in this category.)
- getting a head start on an important world wonder (quite often, you need a head start to beat an AI to a wonder, due to their production bonuses).
As you can see, all of those examples I've listed work very well with bulbing. Getting the tech before anyone else is the key part of all of those. Choosing the right tech can be important, and that's why the Great Person Bulb preference list is so useful. As soon as you see: "Hey! If I won lib and took Military Tradition, I could stomp on Ghandi with Cuirassiers!" You can start planning to get the Great Scientists and peripheral techs you need to pull it off.
Hope that helps!