1 Cubic Meter has 1000 liters of liquid. Meter is a unit independent of Kilogram.
Then why does 1 liter of water at max density (4°C) have a mass of 1 Kg?Is it a mere coincidence?
It is not a coincidence. As the Wikipedia article on the Litre says:
One litre of water has a mass of almost exactly one kilogram when measured at its maximal density, which occurs at about 4 °C. Similarly: one millilitre (1 mL) of water has a mass of about 1 g; 1,000 litres of water has a mass of about 1,000 kg (1 tonne). This relationship holds because the gram was originally defined as the mass of 1 mL of water; however, this definition was abandoned in 1799 because the density of water changes with temperature and, very slightly, with pressure.