Perhaps it is because in 2014, Russia broke its promises and stole Crimea with a military invasion and the west figured they could not be trusted and would almost certainly do the same thing again; which they did.
By the way, how many people died in the Russian invasion of Crimea and resulting occupation? Surely it was very bloody (like the current war) because Crimeans didn't want it, right?
There was never a promise.
>Beset by chaos at home, an increasingly beleaguered Yeltsin turned to historical revisionism. He began to interpret the Two Plus Four Treaty as a ban on NATO expansion east of Germany, on the basis that it only permitted alliance activities on East German territory. He (and later Putin) claimed that the failure to mention Eastern Europe, together with the stipulated restrictions in relation to former GDR terrain, meant an implicit Western rejection of eastward enlargement.
Also later
> At preliminary bilateral talks in Helsinki in March 1997, Clinton refused to respond to Yeltsin’s call for binding restrictions on the establishment of NATO security infrastructure in new member states.
ha ha
"Kissinger confirms US verbal promise to Gorbachev not to expand NATO eastward"
"ha ha" indeed.
"There was never a promise"
Here's a hint: Only one of these two promises would even be relevant.
The promise of not expanding NATO never existed, BUT EVEN IF IT DID then Russia should be invading the US, not Ukraine. There is no justification to invade Ukraine as a defense against NATO, as even if you believe NATO controls Ukraine (it doesn't), taking that land merely increases the size of Russia's border with NATO.
But you know all this.