What was the initial weakness of Copernicus's heliocentric theory before Galileo's observations?

Answer

It lacked compelling observational proof to overturn the established system

Copernicus's theory was elegant mathematically but lacked definitive observational proof; for example, stellar parallax—the expected shift of stars due to Earth's movement—was not measurable then.

What was the initial weakness of Copernicus's heliocentric theory before Galileo's observations?
Galileoastronomyscientistuniverseheliocentrism