Froome's rise is a different issue. There may be explanations for his late and remarkable late blooming, but I can understand the suspicion.
It's not really that late a blooming, is it? He's been among the genuine GC contenders since 2011, when he was 26 and arguably could have won a GT or two by now if he'd been given the opportunity. That's about the right age to bloom - riders have won it younger, eg Fignon, Ullrich, Contador, Schleck, but it's not common.
Before that... well, 2010 was a bad year for him personally with his illness, and a pretty disastrous year for Team Sky in general, so you can't really judge him on that. Prior to 2010, he was putting in some decent performances on a second-tier team. Not being a track cyclist is the main reason he didn't have much of a public profile in the UK prior to 2011 (unlike Barloworld team-mate Geraint Thomas), but he did well in the Giro in 2009, and the British Cycling coaches were obviously paying enough attention to recognise his potential and to want him in the Team Sky set-up.
Anyone who says that he arrived on the podium from nowhere in 2011 is being a little unfair on him. It's not hard to knock down the supposedly "reasonable grounds for suspicion" if you actually look at the facts.
Not that I'm suggesting this is proof that he's clean, mind. I'd just like to see some actual evidence before jumping to conclusions.
[edit: sorry, I'm not having a go at you personally, Hont. I know why you say you can understand the suspicion, and I might have felt the same in the past, but I'm training myself to be more circumspect about interpreting what people say about pro cyclists.]