It is completely random!
As I play on server top now, I also currently have 163% and all my opponents in final phase have 130% max, except one 144%, but even for him it is very hard to win.
In the earlier rounds it was even easier for me, many opponents under 100%. It is kind of unfair for the lower players (I was there before in past seasons), but on the other hand I enjoy it to have one event where it really benefits me for having a strong team and I get something back for it in terms of free rewards if you will. Of course tankers should be excluded from events like this.