Richard III took the throne over Edward V, not by deposition, but by virtue of being of age. Given that Edward IV was likely poisoned by the Lancastrians, it was a legitimate fear. Both Richard and Edward were Yorkists! Having Richard on the throne would protect the kids.
The problem for Henry VII, is that his wife was junior to Edward V and his younger brother Richard. With them out of the way, Elizabeth of York became the senior claimant.
Edward IV died in 9th April of 1483, from a protracted illness, possibly poisoning. Edward V in his will was designated his heir, while the then Richard of Gloucester (later Richard III) was designated the Protector. Edward V was never coronated - Richard took over as King, 22nd of June. The Princes were last seen that summer, but we don’t know when they died.
Follow with me here.
December of 1483 - Henry Tudor agrees to marry Elizabeth of York.
Richard III dies in Bosworth in 22 August of 1485, after just two years on the throne.
Henry takes the throne and then states that the princes were murdered in the tower, and blames Richard III. Of note - he did not state this until after he acceded to the throne after Bosworth. No bodies were produced, nothing. It is possible that the boys were still alive in the tower when Henry VII came to the throne in August of 1485, just two years after the accepted date of their death.
Henry VII would have been 26 in 1483, and 28 when he came to the throne. Elizabeth would have been 17 in 1483.
So, it all fits. Poison Edward IV. Pledge to marry his oldest daughter the year later. Defeat, and kill Richard III, in battle. Kill Edward V and Richard in the tower, before you marry their sister, after Bosworth. Claim, after Bosworth that the boys were missing and that Richard III was responsible.
Ir all fits together, and it makes what happened in this extraordinary 3 year period make sense.
There was no motivation for Richard to kill the princes that his brother left in his will for him to protect. There was every motivation for Henry VII to kill them after his accession.
And don’t forget that Richard did not harm his brother George’s child who was third in line to the throne. Why would he spare the third while killing the first two?
Of course, it was Henry VII who killed George’s son...