The fourth is the market is drying up and your line of management isn’t going to bat for you. Lots of reasons for this and many aren’t personal so no need to personalize it. Many companies try to let underperforming employees go for cause before starting a lay-off because they can avoid the repercussions in unemployment taxes.
This hasn't been my experience, but would love more info if you could provide it.
I'm actually surprised how slowly most tech companies shed staff. In general, it seems the industry is pretty hit-driven, and if you're attached to a good product that's still making money, there's rarely much attrition, even when perhaps there should be. Conversely, a lot of great people get let go when a product isn't working (misses the market or no sales). It all seems kind of arbitrary and random. It's a lot different than, say, a restaurant with really tight margins where you're a day away from getting fired if you aren't perceived to be pulling your weight.
I realized I put two separate thoughts in the same paragraph. When someone is let go in a lay-off it’s often not personal and being a better person might not have saved your position. So it’s probably better not to see it as a personal failure.
Thought 2: if you’re getting let go for performance reasons in a bad time for the company, often they really don’t have performance gripes, but they don’t want to put up with unemployment or file a lay-off, so they let go people that can possibly be fired for performance.