Nothing to do with knowing anything about either as a coach, more to do with seeing what is needed to succeed as a coach, and I'm referring only to what each of them has shown.
Not doubting Toovey's ability, but he's a risk. He inherited a premiership winning team and maintained that before starting to slip away at the end (IMO, that team was never going to win the 2013 premiership anyway). Yep, he's hard nosed, not scared to drop players, etc...sounds exactly like the 'straight shooter'-esque character traits that were boasted in our current coach when he was gunning for the job. Those character traits are all well and good when you take over a top squad, but what we have in front of us in a monstrous rebuild, and Toovey just hasn't shown that he can do that.
Compare that with Cleary. He's got a longer and more diverse career, but he's shown that he can take a struggling squad from the bottom to the top, culminating in a grand final with the Warriors. Yeah, he had mixed results, but he faced a lot more challenges than Toovey did with Manly. Then he was pulled to the Panthers, where he took over an absolute rabble of a club, rebuilt them (including bringing through a number of talented youngsters and despite a horror run of injuries) and took them through to within a game of a GF. He was then let go, allegedly because Gould found out he was in discussions with Souths.
I'm not saying Cleary is the messiah or that Toovey is a dud. But if we were going to rely on either of them, Cleary has shown through his career that he is more suitable to take over, considering the position we are in.
Personally, I'd be tapping the hell out of Maguire. The change he drilled into Souths between the 2011 and 2012 season was absolutely astonishing, considering the minimal personnel changes that took place.