Like all the purported research, it presupposes that there's any credible question about authorship. There isn't. The delusional system about "who really did it" arose in the mid-19th century, without so much as a whiff of it before that. It seems to grow out of pathological elitism common to academic losers.
I think that, most, but not everything attributed to Shakespeare was his. He worked in a theatre group and others probably contributed to works eventually edited and published under his name. I do not think that Marlowe became Shakespeare after his death, but I would not be surprised if he did not die and lived under some assumed name.
Time for bed! Good night!