The passport was in for a long time before Mendrisio, and I think your interpretation is overly optimistic. The passport was in force before the 2008 Tour, and certainly in force before the 2009 Vuelta, the last hurrah of the 'old' Evans, who whined and sulked about perceived injustices rather than going out and righting the perceived wrong, since Cuddles didn't even remotely try to gain time back after his mishap with the neutral service car, and also did his usual job of going too deep into the red on the chase and blowing up (he was in Samu's group even after the botched wheel change, but while Samu then limited losses to a few seconds, Evans dropped far further back - although not by enough to actually make that stage decisive despite what his fans protested for years later as he lost 1'08 to Valverde +8" time bonuses, and was 1'32 down overall. Plus, 2007-8 was the cleaner era, 2009 was the start of a return to dirtier times with Bordry losing his job, AFLD being relieved of testing duty and Armstrong's return.
He (Evans) had a habit at the time of having a go, and if it didn't succeed, throwing his arms up and going "oh well" and then waiting for the race to come to him, resulting in his not acquiring the palmarès his talent level suggested he should. The fact that at Mendrisio he actually managed to win with his move - thanks to a combination of factors including but not limited to the significant strength shown by Cancellara making teams wary of towing him, that Spain had marked the move with Rodríguez who had been in the break earlier and was therefore less likely to be able to respond than Samu and Valverde in the group behind, and that Evans had great legs that day and timed his attack far better than he had in previous races (remembering, for example, Flèche '08 where he was the strongest but went too soon and lost it at the end of the Mur) - seemed to completely overhaul him psychologically.
Now well into his 30s and facing up to the prospect of retiring with nothing like the palmarès he ought to have had, and rejuvenated by a change of scenery (even though the support team he had at BMC in 2010 at least was no better than he had had at Lotto), he went out there and started taking the risks he never dared to before, and it worked. He was handed a once in a lifetime chance to make good on the Tour in 2011 due to a range of convenient factors - the heavily backloaded parcours meaning lots of riders were crashed out before they got to any serious part of the race, Contador doing the Giro which he likely wouldn't have done without the ban hanging over him, long time nemesis Valverde being banned, the Schlecks racing like worthless cowards - and he took it. I thought he'd wasted his last chance to win the Tour in 2008, and said as much.
Evans was a quality rider in the pre-passport era, a quality rider in the early passport era and that cleaner stretch from 2007-8 when the Riccòs and di Lucas of this world stood out like a sore thumb, and he was a quality rider as the sport started to get ever faster and shadier again. I feel the real change in Evans' palmarès is nothing to do with the external factors of the péloton getting cleaner or dirtier and everything to do with the man himself changing in mindset from a man who accepted his fate to a master of his own fate.