You don't need a history teacher to explain that, you need a statistician:
https://en.wikipedia.org/wiki/Multiple_comparisons_problem
Essentially, if you look at a large enough set of parameters (i.e., how many letters in their assassins names, when they were elected, what their favorite color was, favorite sex position, whatever), you have a chance of finding enough commonalities that it looks like an OMG amazing coincidence. There is undoubtedly a MUCH larger set of parameters that don't "match" between the two. (Kennedy probably liked oral, Lincoln was probably a missionary guy). You could make a similar set of OMG coincidences for any two people if you looked at a large enough set of parameters.