Honestly, I was surprised the Russians didn’t seize it when Ukraine went independent. I’ve never expected it to remain Ukrainian.
Its a very good question. The seeds of today's crisis was sown with the dissolution of the Soviet Union - and at the time, the West (certainly its media and most analysts) ignored the Ukraine, Crimea, and the details of how the Soviet Union collapsed.
In order to oust Gorbachev, who wanted only reform, not dissolution of the Soviet Union, Boris Yeltsin needed the support of powerful political figures at the time - one of whom was Leonid Kravchuk, the head of the Communist Party in Soviet Ukraine. As the organs of the Soviet state and army collapsed and chaos ensued, "Russia" was in no position to demand anything from the local officials of the Ukraine, Belarus, Kazakhstan, etc... This is the "disaster" of collapse that Putin referred to.
It took 20 years to turn the tide - and now Putin (and Russia) no doubt have re-union with Belarus in their vision as well.