"Khalid Masood was also known by a number of aliases." Why did he need multiple aliases?

We used to live in beautiful England, it was British, classic England. This is what is happening now in Luton, UK:

https://www.youtube.com/watch?v=f8WVkbXOHfM

We are not talking 'lone wolf', we are looking at entire British towns that are turning Muslim. With these results.