It is only more believable because we have got used to seeing Bolt for years running at this high level.
I can see Bolt has got natural ability, but the massive improvement from 2007 to 2008 is very suspect.
Bolt had a lot of pressure from the media in 2008 after these crazy performances, people constantly asking the drugs question. Then, after he won the Olympics with 3 World Records, 9.69 with hands down 15 meters before the line, in 2009 the drugs question went away completely from mainstream media and all of a sudden he was clean.
I believe the same will happen with Yoyam Blake. This will be his breakthrough year, crushing Bolt and people will say how is he doing it, then next year in 2013, he will be "clean" again to the media like Bolt was.
Also, in 2009 when Blake got busted for some banned drug and got like a 6 months ban, I remember the BBC saying how a Jamaican was busted, but it was not one of the "big names". Well, now he is one of the big names, but I can guarantee you will never hear about that 2009 ban on BBC or similar so close to their precious Olympics. They do not want to remember how the potential Olympic Champion for 2012 was in 2009.
http://www.guardian.co.uk/sport/2009/jul/26/jamaican-athletes-positive-drug-test