I agree, it's the drying and curing that makes it "brick weed"

Basically brick weed is what happens when you cure cannabis in anaerobic conditions (ie when the buds are still wet), and then press it into bricks for easier transport. When you break open the brick, often you can barely tell what's bud and whats leaves or stems.
For example some outdoor growers will throw newly harvested cannabis buds in a pile while wet, (leaves, stems, bugs and all) and let it cook in place like a compost pile. After some amount of time, the buds are wrapped up and compressed for storage, often still partially wet, then cut up into bricks. This is considered a type of "brick weed" and is often "harsh" to smoke.
If the starting cannabis is bad, the result will be, too. But some people actually prefer the effects you get from bud cured in anaerobic conditions when you start with good bud. For example, some indoor growers put their buds in jars while at least partially wet on the outside, causing extra bacterial growth.
Example of bud cured in anaerobic (wet) conditions
Any curing process that involves letting buds stay wet and sealed up at the beginning produces weed with a different consistency and different effects, though sometimes buds can be more harsh. Buds become crumbly and they lose their green color after just a week or two, becoming more tan or golden. This type of bud is considered "inferior" by some people, especially in areas with dispensaries (where most of the bud is green and barely cured). However, there are people I've met who prefer this type of cannabis because they like the slightly different effects.
That being said, curing buds while still wet can be unsafe by causing unwanted mold or a bad type of bacteria to grow. If you cure buds while they're dry on the outside and moist on the inside, as with traditional curing, you can achieve many of the same mental and physical effects of anaerobic-cured weed without the risk, simply by giving buds more time to cure.
If you want to safely get the effects of anaerobically cured bud, you can cure buds the traditional way for 2+ months. As regular buds continue curing, they start to slowly get a similar appearance and consistency of bud cured in anaerobic conditions, but instead of being harsh they actually get smoother over time. The mental and physical effects of long-cured buds also seems to get stronger as it's cured longer (up to a point), giving similar heady and body effects that some describe as being a little "drunk." Long-cured buds gives you the same benefits without the harshness or lack of safety!