There can’t be any doubt that Maynard did a cracking job at part time Wealdstone, and obviously he’s very well regarded there. The question is whether that qualifies him to make the big step up at a club like Notts.
There must be some recent examples of a previously part time, non league coach taking over an hopefully upwardly mobile EFL club and being a success, but I don’t know of any. The closest I can think of is the Cowleys at Lincoln, but they were on their arse still in non league, so it’s not that great an example after all…
Brady at Northampton managed at Brackley town a few years and then took over Northamptons u16s and 18, Curle got sacked, he took over interim and they got relegated.
Surely they didn’t give him the permanent job, they did, playoffs next season, lost them, promoted the season after and now mid table this season.
He did get Brackley promoted and reached the 6th tier play off final the following season. Not exactly earth shattering but at least that's something.
Also, based on a 3rd tier table from the day he took over from Curle, Northampton would have stayed up, so not an entirely crazy decision to give him the job full time.
There's always the odd caretaker who makes a success of it, just by being in the right place at the right time, otherwise they wouldn't get anywhere near the job.
The Northampton boss didn't get the 1st team job because of what he did in non-league the previous decade. They sacked Curle's assistant at the same time, so he would have been the last person left to take hold of the reins whilst they looked for a replacement. Presumably he was a popular enough character with the players to justify sticking with for longer and he's turned out to be another one of those happy accidents, like Nigel Adkins who joined Scunny as a physio having previously managed Bangor City, got into the hot seat as caretaker and ended up managing in the Premier League.
Honestly, I think you could literally grab random supporters off the terraces and put them in the dug out and one or two would somehow have the personality and natural leadership skills to hit it off with the players and fans and get something going. Probability wise though, to give yourself the best chance of success you look to appoint somebody with experience of navigating their way out of the situation you're in.