Why exactly did Henry VIII preference the Grey line to the Stuarts?

[Barnes]

In Henry's VIII's much-maligned will, he specifies that if his three children should fail to produce any heirs, the succession would pass to his younger sister Mary, Queen consort of France, (or really her heirs, as she was dead by this point) over that of his elder sister Margaret, Queen consort of Scotland. Now, this as well as a few other things provoked the "Grey succession," as we all know, but I'm wondering why this was instituted in the first place? Was there really that much of a concern over a union of the English and Scottish crowns? I mean, I understand it wasn't exactly the most preferred situation, but it all seems rather odd.

[True Federalist (진정한 연방 주의자)]

Religion most likely.  At the time of Henry VIII's death I believe the Stuarts were still Catholic, whereas Mary Tudor's children by her second husband, the Duke of Suffolk, were all stunch Protestants.

[Barnes]

Religion most likely.  At the time of Henry VIII's death I believe the Stuarts were still Catholic, whereas Mary Tudor's children by her second husband, the Duke of Suffolk, were all stunch Protestants.

That seems the most likely reason, and yes the two separates lines were both strongly divided by religion.  Thanks.

[MASHED POTATOES. VOTE!]

Religion most likely.  At the time of Henry VIII's death I believe the Stuarts were still Catholic, whereas Mary Tudor's children by her second husband, the Duke of Suffolk, were all stunch Protestants.

That seems the most likely reason, and yes the two separates lines were both strongly divided by religion.  Thanks.

Religion (along with the Duke of Northumberland's desire to stay in power) was the reason they tried to bypass Mary with the Grey line after Little Eddie's death. Didn't work well.

Interestingly Lady Catherine Grey, poor Jane's sister, was initially considered Mary's heir in place of Elizabeth, which didn't work too (although not so dramatic).