It's amazing what happens when you choose primary sources instead of opinion pieces. Tey uncovered something extraordinary: Henry VII had an extremely dubious claim to the English throne, so the "murder" of the two princes in the tower should have been front and center when he returned from Bosworth, stolen crown in hand.
There are, in fact, no contemporary accusations against Richard III for murdering his two nephews. Murdering them, in fact, would have barely had an effect: there were at least seven or eight heirs in total, and Richard took precisely zero actions against them. Under Henry, they all died or were executed or exiled. Upon hearing word of his brother the king's death, Richard went into mourning, paid for a requiem mass......and proclaimed his fealty to his nephew the new king. Then he.....stayed where he was. Surely a would-be regicide would make haste to seize power, wouldn't he? In fact, Richard made arrangements for his nephew's coronation, up to and including mundane things like fabrics and invitations.
It was the Queen's ne'r-do-well brother who galloped to London in haste.