Never said it was an accident at all. What I am saying though that any well formed character given as much page time could find the same levels of popularity.
You're ignoring that Aunt May chronologically debuted before them both and is more integral to the formation of the Spider-Man mythos than either. Peter will have different bosses and different girlfriends but he will always have one sole guardian (ignoring AUs, of course).The two Spider-Man supporting characters with the most appearances across all Marvel comics in 616 is J. Jonah Jameson and Mary Jane Watson both over 1200 each with MJ maybe overtaking Flat-Top and at different times being ahead and behind.
Aunt May hasn't even reached 1000 and is a distant third.
Which is all very much besides the point of the thread, I may add.
Can't even make a joke without people looking to (unsuccessfully) make a "gotcha".