It should be spelled with a hyphen, "co-opted." It means to deal with opposition by bringing your opponents into your group.
I can't explain your sentence because I don't have the background, so I'll use a different example. William H. Seward ran against Abraham Lincoln for the Republican nomination for President. He was Lincoln's opponent. He lost. Lincoln became President. Even though Seward had been his opponent, Lincoln appointed him to the position of Secretary of State. It's one of the most important offices in the USA government. Seward couldn't refuse. Now that he was part of Lincoln's government, he couldn't oppose Lincoln any more. Seward had been co-opted.