Correction of the paragraph of PC II

Hey there! So, Wednesday we got back our writing parts of the second Progress Check. According to my English teacher, I can be pleased about having improved 12% after the first PC. However, as I was having a look at my text, I realized that there is still a lot which needs to be corrected and- as always- I made some unnecessary errors. Here is my correction:

While there is an obvious connection between these two items, there are also a number of significant differences. The Vikings, as well as the Plantation Settlers caused changes in Irish history. To be more precise, they arrived from abroad, drove many Irishmen off their lands and settled down. The Vikings settled on the east coast. In the beginning, they tolerated Irish Catholics. Some of the settlers even converted to Christianity. Nevertheless, they killed Brian Boru in the Battle of Clontarf. Not without reason they are known to be brutal killers and their "hit-and-run" tactic in plundering the monasteries which were known to have money and supply. Therefore, the Vikings were seeking a better life and wealth. The cause for the settlement of the Plantation settlers is completely different. The Britons aimed to have control over Ireland. In their opinion, the only way to achieve this goal was to plant settlers in Ulster in order to drive Catholics off their land and to spread Protestantism. Therefore, the Plantation Settlers were sent by Westminster to accomplish this mission. They were successful and stayed in the North. In Summary, there are more crucial differences between the Vikings and the Plantation Settlers, than similarities.

As, always, I would appreciate some feedback of you, what can I improve and what was fine.
Thanks!

Have a nice weekend!