European climate means that migrant from Africa become paler-skinned over many generations. The European climate also means that agriculture is necessary to feed a growing population, but also requires more effort than other climates. The geology of Europe provides easier access to materials such as flint and copper to make better tools. Better tools give acess to tin (for bronze) thern iron and coal (which eventually produce steel). Ultimate outcome being that the people with the pale skins also have the more advanced tech, including ocean-going ships and powerful weapons.
This allows Europeans to go looking for exotic raw materials elsewhere (the Silk Road was great, but it took an awfully long time for ther merchandise to hit European markets. So they went to place they'd never been and found lots of stuff they could buy and sell. But then the local bigwigs they were trading with started saying things like "D'you think you could take a few of your lads with their bang-bang sticks and do something about That Lot Over There? The ones that keep raiding our fields, kidnapping our women and refusing to worship the right gods? We'll make it worth your while...?"
Or trade kept getting disrupted by Tribe A and Tribe B having their annual war. So poor old Tommy Atkins and his mates get called over to sort it out once and for all!
Between using the powerful, disciplined European armies as tools to bolster their own power, clinging to irrational, ancient feuds and often just being too chaotic and corrupt to conduct trade properly, far too many non-European cultures virtually invited colonisation. This led to costs for the colonising nation, which had to be recouped by increasingly brutal exploitation of the colonised. A vicious circle which gave rise to aggressive imperialism and the concept of White Supremacy.
"Nothing is evil in its' beginnings, even Tony himself was not so." As the saying goes. The whole thing started out with merchant adventurers and ended up with the mess we're in now. Not so much a case of "Let us build empires based upon our holy whiteness and God-given superiority!" More "FFS! If the locals can't sort this mess out for themselves, then we'll have to do it for them or we'll all be bankrupt!"
