According to Muslim gnostic commentators, sufis or mystics, the first thing that Allah created was the light of the Holy Prophet. This idea is backed by various Islamic traditions a most notable one being a hadith by the Prophet that reads: "The first thing Allah created was my light."
This and many other hadiths with similar theme have been subject of interpretation and discussion among Muslim gnostics and philosophers. Muhy ed-Din Ibn Arabi who is arguably the most prominent Sufi/gnostic commentator has extensively discussed the implications of the idea of the existential precedence of the Holy Prophet's Light over creation.
Now when the theory of the existential precedence of the Prophet's Light is considered in conjunction with the theory of Emanationism -- another widely accepted theory by Sufis and Muslim meta-physicians which basically suggests that each level of creation emanates from the higher, preceding levels -- it follows that as Prophet Muhammad's light precedes every other created being according to the hadith, no other creation could've been created if the Prophet's Light had not been created first!
Also according to theory of Emanationism, the existential precedence of the Holy Prophet over the creation necessitates his superior merit, nobility and excellence over them all. That is the prophet is the first of creation, the best of creation and therefore the most beloved creation of Allah!
Now Shiites come in and cite a lot of traditions from the Holy Prophet and his special, most beloved family members that they define as the true Ahl al-Bayt, suggesting that they are also of the same holy primordial preceding substance of the Prophet, of the same 'light', upon whom other creations depend.
Now to conclude it all and answer your question, Allah loves all of His creation but loves the first and the best of them the most, and this explains why it would've been impossible for the universe to be created without the creation of the first and the most beloved beings to Allah. (As a side note, this impossibility is based on the governing laws of creation that emanate from the very Allah's existence).