those angles) it is the responsibility of the runner to avoid the fielder. That means it's the responsibility of the runner to FIND the fielder and avoid him. The runner made no attempt to find the fielder so he could avoid him. Even if what you say is true that the fielder started on the wrong path, it's still the runner's responsibility to avoid him. If the runner is watching the ball in order to determine where to go to avoid the runner, then he risks an interference call by not knowing where the fielder actually is.

As to your belief he changed direction after locating the fly - it seems apparent to me that the fielder had eyes on the ball well before he changed directions. The jump to his right was entirely to avoid contact. Even then, it looks like there was contact between the fielder's right hand and the runner's hip as the fielder tried to "swim" past the runner.

If there's actual contact or even near contact, that call has to be made.