The Solar System and all of the visible stars are in different orbits about the core of the Milky Way galaxy.
Thus, their relative positions change over time, and for the nearer stars this movement can be measured.
Canopus has persistently been the brightest star over the ages; other stars appear brighter only during relatively temporary periods, during which they are passing the Solar System at a much closer distance than Canopus.
[1] Jocelyn Tomkin used this data to compile a list of brightest star in Earth's night sky at each period within the last or next 5 million years.
For example, it omits Gliese 710 which in about 1.35 million years is expected to be close enough to have a magnitude of −2.7,[2] as confirmed by the Gaia spacecraft.