Dunno.
All of Irons, Hopkins and Burton have made what might be termed "paying the bills rubbish". Why not commit to a Bond movie every couple of years which, after all, may well be rubbish but pay the bills most handsomely? None of the three can claim they made every movie or TV series purely out of artistic integrity. And, of course, we know Burton had agreed to play Bond for McClory in THUNDERBALL before McClory and EON deccided to make the film together... But of course the point is mute; we do not know if EON at any stage would have been interested in offering the Bond role to them anyway.
Lots of paying the bills rubbish, no arguing that. But for the most part only once their class was established and there really was no doubt about their potential as actors.
Didn't know Burton agreed to play Bond in McClory's project, I always assumed he wasn't interested in the part.
The best example I can give of the appeal of Bond to a "proper" actor is Tim Dalton. By 1986 Bond had been taken down the comedy toilet as far as it was possible to go, and, I suggest, into a a far bigger hole - far less cool or popular - than it was after DAD. And yet Dalton took Bond on despite it being in that state, and despite the fact that Dalton had an extremely successful theatre career. Simply because Bond is a far more appealing deal, both financially and professionally, than garbage like CHARLIE'S ANGELS, SINS, MISTRAL'S DAUGHTER, BRENDA STAR, etc.
I don't think this is a question of garbage entertainment vs serious art. Dalton undoubtedly had the look, the basic understanding and the potential to become a great Bond, and I think he knew that perfectly well. The only question would have been the right point to take it - if it's still on offer, that is. I think he took it at just the right moment in his career but was decades ahead of his time for the Bond series itself. But the simple fact is that at the time he became Bond he didn't have prove anything any more in terms of his acting.
I maintain Craig was in exactly the same position in 2005. Bond gives a security and position certainly LARA CROFT and THE INVASION do not, nor evn LAYER CAKE and MUNICH. As I suggested earlier, even Craig's great guide, Steven Spielberg, makes commercial rubbish these days with no greater artistic value than DAD. Craig was never likely to turn Bond down when the offer was made finally to take the part.
Craig ran a much higher risk and could well have become the last Bond for a time. And flicks as LARA CROFT and INVASION would soon be forgotten when the last Bond film for a given time would be a thing people would remember for a very long time.