Why did they air all four Tsukimonogatari episodes in one day?
The reason why Hanamonogatari was all aired on one day was because it kept being delayed because of production issues, it was supposed to come out the Spring season but ended up airing at the very end of Summer season (basically the Fall season). The studio decided to delay it no longer and release it all at once.

See this ANN post

I'm not sure of the exact reason for Tsukimonogatari's bulk airing, but it could be a related reason.