Intel tends to use the same socket (and therefore maintain mobo compatibility) for 2 generations, the first one being a new architecture, followed by a die shrink. Sandy Bridge and Ivy Bridge. Haswell and Broadwell (although I seem to remember Broadwell support with 8 series chipsets being iffy at best). Skylake is a new architecture, with a new socket. It remains to be seen how this pattern will play out now that Intel has abandoned their traditional tick-tock (new architecture, then die shrink) pattern. Normally, it would be assumed that Cannonlake (die shrink) would work with Skylake chipsets, but with the introduction of Kaby Lake in between, nobody can say for sure.
But long story short, no one but you was expecting Skylake to work on Z97 boards.