I believe the answer is:
They did not have the most advanced military equipment.
There was a lack of unity among members of various groups.
They were weakened by trade restrictions and blockades
The difference in millitary equipment made the colonised country unable to defend themselves in the face of Europeans threat
. When this happen, some people decided to surrender to the European while some of them decided to fight, which divide the unity among them. Not only that, if the majority of people refuse to follow the colony, they would be given with restrictions and blockades which hurt their economy.
