Observe how the rejoining aircraft is under control, and performing a slow controlled rejoin with lead. The rejoining aircraft isn’t on a collision course with lead, but on a parallel vector and is lower , climbing slowly up the rejoin line with a controlled closure rate. Closure rate is difficult to gauge and it’s easy to misjudge until it’s too late. That’s why we paractice closures a lot.
Aerial refueling and hooking up to a tanker wasn’t as difficult as coordinating a rendevous with the tanker and joining up with him to get the gas.