TSMC Often Appears Fully Booked
TSMC plans and builds fab capacity based on orders. Orders take 12-30 months to build, depending on wafer/chip complexity, and process node maturity.
TSMC knows what's coming down the pipeline years in advance, so they appear to always be booked for leading edge processes, and if a customer unexpectedly increased order (Nvidia/AMD), TSMC adds capacity as required.