This is my point too.Not getting a centre forward is obviously a major failing, but there are just too many plausible explanations.
Why didn't we bring one in?
Could we not convince players to join? Did our valuation not meet the selling club/player's wage demands? Our search seemed to focus on target men, was Koeman unwilling to compromise on that? Did Walsh suggest a number of players but couldn't convince Koeman of their worth? Did we ultimately decide that a strike force of Rooney, Sandro, Calvert-Lewin (and Niasse?) was enough to see us okay? Did we decide that developing Calvert-Lewin was a better option than signing the target man 8th down our list? Could we not afford one? Did we dwell too long on our number one choice when it might have been more prudent to wrap up a young potential target man early on as a back up just in case?
We can probably answer a couple of those from interviews and journalist mutterings, but most of them haven't been addressed at all.