noob question - why does one bulk? if it is to lift heavier weights, another noob question, why would being heavier help you lift heavier?
Baisically it 'guarantees' muscle growth. To grow muscle in the most effective way, you need to be consuming more calories than you need. Put simply, bulking is consuming more calories than you need, and cutting is consuming less calories than you need.
Some people go over the top and 'dirty bulk' which is going way over this calorie limit by eating McDonalds and eating other general crap. The proper way to do it would be to count your macros and have proper foods, although this takes a lot of dedication.
Well you hope what is making you heavier is more muscle mass
So more muscle = lifting heavier