We came, we took their land and subjugated them. It’s not a mystery of any sort... Sadly, they were easily subjugated because they were essentially stone aged people fighting against European’s with flintlock muskets, horses and swords... Three things the indigenous people of North America didn’t have when Columbus and other explorers arrived in North and South America.
They have been abused and mistreated for centuries... That’s they way it goes... Just ask the Irish, Scottish and other communities that were subjugated by the British. You just need to suck it up and get over it.
Ask the Ukrainians, for that matter.