Multiple reasons. A perfect storm. Covid interrupted supply chains. Companies in general thought that there would be a covid recession and cut orders. Demand increased instead and there isn't enough capacity to catch up. The drought in Taiwan. Making chips requires an insane amount of water. The Taiwanese prefer that their populace not die of thirst. Go figure. Helicopter money from the Fed, which is probably why demand increased. A simple matter of more dollars chasing fewer goods. Other than the drought in Taiwan, these factors all play into the other shortages, and each of those may have it's own contributing factors. Like lumber. We have plenty of wood. What we don't have is sawmill capacity or the willingness to invest billions to build more capacity which might come online just in time for the next recession. Complex systems don't handle disruption well ...