You have 1mbps, but you very, very rarely actually use all of that. It doesn't actually really matter if everyone had 1Gbps internet connections, because most everyone is requesting data so infrequently that the points that must bear all the load can handle it.
Pretty much, 100Gbps is about 100 thousand times your internet connection. So, a single 100Gbps line could handle 100 thousand people like you requesting a 1mb file at the EXACT same moment. Spread that out by even a few seconds and that router can handle way more people than that 100 thousand.
This is a GROSS oversimplification, but the idea stands.
Pretty much, 100Gbps is about 100 thousand times your internet connection. So, a single 100Gbps line could handle 100 thousand people like you requesting a 1mb file at the EXACT same moment. Spread that out by even a few seconds and that router can handle way more people than that 100 thousand.
This is a GROSS oversimplification, but the idea stands.