Suffice to say, the Rail Accident Investigation Branch is extremely thorough and will cover all aspects of how the track in the area was managed, observed, inspected, and so on. There is a reason the reports take about 12-18 months to produce, when it takes mere minutes or hours to establish a few facts (speed of train, point of derailment) and a rough cause (permanent way defect). There is also a reason why accident investigations no longer have anything to do with the HSE.
The Lewes derailment happened 22 hours previously. Even if the kink in the track which caused the derailment was visible and actionable then (which I doubt given what has been posted upthread by some highly experienced people, but we'll see what the RAIB say), it is impossible to check every single piece of track in the country in 22 hours while keeping trains running.
Another part of the reason that the minutiae of track reports aren't and won't be made public is that, based on what I've seen of them in RAIB reports, they are exceptionally boring and hold little to no useful information for a layman such as I.
Obviously the wait for a public report is a tense one. I'm mildly concerned about the three relatively serious incidents so far this year, and I know how vanishingly rare such events are and how safe our railways still are. So I do appreciate that the thirst of the general public would be easily satiated by an update. But just because we see nothing doesn't mean there is nothing: other internal reports will be produced that perhaps don't grind quite so fine as the RAIB but will at least result in action being taken.
It's not as if the railway wants these derailments to happen, given it has terrible public image problems even when it hasn't suffered two potentially very bad derailments in two days. And the "solution" that appears to have been put forward on this thread, for a report to be thrown together in five minutes flat saying "track fault, make sure it doesn't happen again", ignores the fact that the first principle of railway safety is to investigate the incidents of now to prevent the disasters of tomorrow.
Finally, for the record, while I would be surprised if the weather wasn't a factor in both incidents, I would also be surprised if the root cause of the track irregularity at Wickford was the same as the root cause of the track irregularity at Lewes - as Annetts key says, the permanent way is extremely complex.