1. This is done so that the functions of google and Alphabet X splits and the burden is comparatively minimized on a single company, making the companies focus more on their core functions. And the fact that Alphabet X does not involve search function is because Google already has the largest market share for search engine. So, this is done to have google maintain the market share for its search engine.
2. Google already has a very huge market value and is trusted by people worldwide. As per Larry Page “We liked the name Alphabet because it means a collection of letters that represent language, one of humanity’s most important innovations, and is the core of how we index with Google search! We also like that it means alpha‑bet (Alpha is investment return above benchmark), which we strive for”. However, this move might be to provide visibility to investors regarding the operations of Alphabet’s new acquisitions. This will help in building up trust in the eyes of the investors and making them believe that Alphabet can make profits from the new markets in which they are stepping on.