The Princes were killed.
Who had a motive to do the deed?
Who had the power and opportunity to carry it out?
Looking bad for Richard III.
However, The Tudors were able to write the history books and send certain evidence down the memory hole. Consider what Barack Obama has been able to do with much less power that belonged to the Tudors.
Please show me the evidence that Richard of York and Edward the 5th were murdered. Not even Dan Jones, Richard Starkey or the rest of the Tudor historians claim that the princes were killed. They suspect it, yes, but they cannot claim it. There is simply no evidence.
Richard III had zero motive for killing the princes, they’d been delegitimized by the Titulus Regius.
Henry VII had the children of Richard’s elder brother relegitimized and the Titulus Regius copies burned (one happened to survive in obscurity and was rediscovered in the past century), so he could (and did) marry their sister, but the princes obviously had a better claim at that point — apart from the fact that he’d already had them killed.