There's been a number of plausible theories proposed as to why there may be good reasons for taking these 5 other cases on first before going in with the MM charge. At the moment though, they are all speculation and ultimately we can only go off the official reason given by HCW; that they already have a case strong enough to bring an indictment but they feel they can potentially strengthen it further with time on their hands. His position from Oct 21 makes total sense to me -
Speaking exclusively to the Mirror, German prosecutor Hans Christian Wolters said: “It is now possible that we could charge. We have that evidence now.
“But it’s not just about charging him – we want to charge him with the best body of evidence possible.
“When we still have questions, it would be nonsense to charge rather than wait for the answers that could strengthen our position.
“That’s why we said we’ll investigate as long as there are leads or information for us to pursue. I’m not saying that what we have is insufficient now. But he’s in prison, so we don’t have this pressure on us. We have time on our hands.”
Madeleine McCann prosecutors say they have no body and no DNA but other evidence leads to only one conclusion - jailed rapist Christian Brueckner is guilty and could be charged next year
www.mirror.co.uk
In the 5 other cases, they have obviously taken those investigations as far as they can realistically go. In the MM case they clearly believe there's more leads they can continue investigating and in ideal world, they would obviously like to recover the body before charging. While there is still a chance of that happening and there is no time pressure on them to charge, it makes sense that they continue to investigate in the hope of a breakthrough, or at least gather more evidence to help make a conviction more certain. It might only take one small thing, such as a sighting of CB perhaps, to help with that.
Just purely as an example, lets say they have evidence that points to MM's body being put in a well. They can't really ask the PJ to go searching every well in the Algarve, there's thousands of them. However, if some new info came to light that puts CB in a specific location, in the time frame they believe CB disposed of the body, that may be enough to convince the PJ to undertake another well search in that area. JMO.