It would be accurate to just say "pandemic". The detailed answer some may be curious to know:
1. Lunar new year production shutdown early in the year
2. Pandemic shut down of factories, exacerbating #1
3. Air freight cost increase, PC parts were previously shipping on passenger flights. But passenger flights way down.
4. Boat freight cost increase or unavailable due to medical supplies taking priority
5. Stimulus checks in USA increased demand for PC parts. Increased demand surprised suppliers as this is seasonally a low demand time of year.
There is also discussion of some parts being in supply but the companies can't get them to stores due to a lack of transport options. Not a good time to build a PC, unfortunately.