What does Mr. Logan mean when he says this things been coming a long time baby and TJ just happened to be foolish enough trigger it

Mr. Logan is talking about the racial divide and tension between the white landowners, sharecroppers, and business owners. TJ didn't create the tension, but his actions brought the feelings of both sides to a head. Eventually, the conflict would have come t the forefront regardless of any one person's actions. None-the-less, TJ's involvement in the beating of the Barnett's exacerbated the situation.