How is the EB-1 visa faster than other US visas?

For most persons it is faster. The State Department puts out a Visa Bulletin each month announcing what dates can move forward toward permanent residency. Your Priority Date is the date you start your permanent residency case. As you will see in the
Employment categories the EB-1 dates are most favorable (other than some of the EB-5 categories).

In terms of timing, that’s partly true: the EB-1 classification allows for premium processing of the I-140 petition, and the priority date is generally current or subject to shorter periods of retrogression, depending on the country of chargeability. Success, however, is never guaranteed—after all, very few things in life are certain, aside from death and taxes.

Depending on your country or birth and case strength, it may be a faster option to obtain a green card. EB1 category is the first preference employment-based category, which does not require lengthy labor certification process (knows as “PERM”) and for most countries does not have a visa availability backlog.

When an applicant truly meets the very high evidentiary standards, an EB‑1 case could move faster than most other employment because there is no labor certification required, one can pay for premium processing, and priority dates are usually current.
However, keep in mind that speed does not guaranteed approval, premium processing only covers the I‑140 stage, and that the criteria for this visa are very strict.
Avoid anyone who guarantees EB‑1 approval.