Why was his Bristol statue toppled?

In the United Kingdom and the United States, statues linked to slavery are being toppled as part of the Black Lives Matter movement. Now, there are demands for the same thing to happen in Australia, with monuments tied to the degradation of First Nations people to be removed.

Protesters throw a statue of slave trader Edward Colston into Bristol harbour, during a Black Lives Matter protest rally, in Bristol, England. Source: AAP