That's a leap of astronomical proportions. Why was Kennedy required to be assassinated at 12:30 PM (CST) on 22 November 1963?
This is a favorite LN strawman (employed particularly often by "Richard" "Strawman" "Smith"). Assume that a conspiracy necessarily means that every minute detail of what happened that day and every day leading up to it had to be meticulously planned in advance and it could only have happened that way.
You miss the point John... not surprisingly.
Most of the conspiracy books (and internet JFK Conspiracy pundits) posit Lee Harvey Oswald as being placed in the TSBD as an employee by conspirators. This is so he could be framed as the assassin of President Kennedy (on 22 November 1963).
Oswald being an employee due to happenstance (or coincidence if you like) fits with him being the sole shooter who assassinated President Kennedy.
Incidentally: If Oswald does not get a job at the TSBD, President Kennedy leaves Dallas alive. Don't give me that "a backup plan was in the works" nonsense. We can only deal with the historical record. Accordingly, "No coffee for Randle, no job for Oswald -- at the TSBD" means that President Kennedy would have lived to complete his first term and probably would have been elected to a second term as President of the United States.