Several things puzzle me about Wyatt's Rebellion, & one's Henry Grey's involvement. He'd already been pardoned by Mary (Frances Brandon allegedly prostrated herself at Mary's feet to beg for his life, though she couldn't be bothered to inquire about Jane's) for his role in Northumberland's conspiracy to place his daughter on the throne in Mary's stead. Wouldn't you'd've thunk he would have retired quietly to the country & kept his nose clean rather than risk incurring Mary's wrath again? Why would he involve himself in a plot to wed Elizabeth to Courtenay & shove Mary aside for that, when certainly Elizabeth wasn't his own daughter. What was in it for him? Acknowledgment of Jane as Elizabeth's heir presumptive wouldn't've been a sure thing, especially with the plot's focus being Elizabeth's marriage (& subsequent breeding of heirs to follow). He had to have known if he failed, Mary wouldn't be so forgiving of a 2nd effort on his part to dethrone her, & she wasn't (methinks she was rather mean to execute Jane before Suffolk, tho I reckon Jane's parents didn't much care anyhow). So why stick his neck out for Elizabeth & Courtenay?
Courtenay was the weak link, & he was the one who spilled his guts about the plans before Sir Thomas Wyatt ever left Kent. After being raised imprisoned in the Tower from age 11, one would've thunk he would've wanted to be king out of sheer revenge if naught else, & since Mary was determined on Philip to wed & not him, here was his chance to marry the other Tudor claimant & rule anyhow. What made him open his mouth & spoil it all? Was he one of those peeps who couldn't handle "life on the outside" after such a lenghty imprisonment, & WANTED to go back to the security of the Tower?
Elizabeth famously made a remark to the effect that Wyatt may very well have written her with the details of his plot, but that didn't mean she'd received his correspondence. As its centerpiece, is it likely that Wyatt would've proceeded if she weren't advised of the plans & willing to cooperate in them? It's said that the aftermath of Wyatt's Rebellion was the only time Elizabeth really feared for her life, & had one shred of evidence come to light, Mary would've made an end to her. Certainly Gardiner was frustrated at the inability to directly link Elizabeth to the conspirators. Was Elizabeth clever enough to outwit her interrogators, or was she truly as ignorant as she pleaded?
Finally, there's Wyatt himself.....what was he thinking? He knew Courtenay was singing like a canary, & that moving up the date was a disaster waiting to happen as his co-conspirators were all in a muddle at Courtenay's betrayal. His father narrowly escaped putting his head on the block when he was rounded up in the Boleyn downfall. Did he think charging ahead was better than either fleeing the country with his head intact, or sitting home at Allington waiting to be arrested?