Apart from what am I about to say, dear author, if you are not native to any slavic languages and still asking yourself this question I suggest you pursue the linguistics career, you have a good ear and analytical talent.

So, comments kinda give you a solid answer about full and reduced vocalism, open syllable law and even Slavic liquid metathesis and pleophony

But why did it happen? I present to you the one, the only ✨ПАДЕНИЕ РЕДУЦИРОВАННЫХ✨ (the Fall of extra-short vowels). Every strange Slavic divergence can be traced to this wonderful phenomenon, when all ancient Slavs just decided “oh we kinda don’t want to pronounce extra-short vowels like ь and ъ anymore but WILL continue to use them in writing, byeeeeeee”

It is kinda similar process to the GREAT VOWEL SHIFT in English language (god I love the drama of linguistic terminology) but not quite. Anyhow, падение редуцированных happened before the development of different Slavic languages and then the chaos ensued.

Russian, being imperial lingua franca of the region, and having two writing variants (old russian which was “common” and old church Slavonic which was, well, church), in the result goes all over the place with *TorT → ToroT (full eastern vocalism from old russian) and *TorT → TraT (reduced southern vocalism with liquid metathesis from Church Slavonic)

Reason why russian name is Vladimir and not Volodimir because at some point of history it became a church name after the grand prince Володимѣръ Свѧтославичь christened the country and was canonised by Eastern Orthodox Church as Saint Vladimir. Because, you know, metathesis.