All of the components in the supply chain will be rated for greater than max load, however power generation at grid scale is a delicate balancing act.
I’m not an electrical engineer, so the details here may be fuzzy, however in broad strokes:
Grid operators constantly monitor power consumption across the grid. If more power is being drawn than generated, line frequency drops across the whole grid. This leads to brownouts and can cause widespread damage to grid equipment and end-user devices.
The main way to manage this is to bring more capacity online to bring the grid frequency back up. This is slow, since spinning up even “fast” generators like natural gas can take on the order of several minutes.
Notably, this kind of scenario is the whole reason the Tesla battery in South Australia exists. It can respond to spikes in demand (and consume surplus supply!) much faster than generator capacity can respond.
The other option is load shedding, where you just disconnect parts of your grid to reduce demand.
Any large consumers (like data center operators) likely work closely with their electricity suppliers to be good citizens and ramp up and down their consumption in a controlled manner to give the supply side (the power generators) time to adjust their supply as the demand changes.
Note that changes to power draw as machines handle different load will also result in changes to consumption in the cooling systems etc. making the total consumption profile substantially different coming from a cold start.