MW development is a whole job in itself. From experience; it's hard to work meaningfully on a major project (such as that) whilst also doing smaller bits of work (like outreach, sysadmin, smaller development tasks).
Why is that, out of interest?
But anyway - Mike has posted the Board's reasoning here, and I will only echo part of it - which is that the "developer" post has been under discussion for about 18 months, and it is long overdue that we advertised it one way or another.
Chris