No one forces Russia to attack its neighbors.
As long as Russia insists on waging war against its sovereign neighbors, Russia is a threat to Europe.
WW2 didn't have to happen, and the UK and France could have interviened sooner, before the Nazi war machine took over the Czechs, the Poles, etc.
ounce of prevention vs. a pound of cure
According to your theoretical, Russia could attack and immediately invalidate Ukraine's ability to join NATO by re-triggering a conflict.
Come on is this stuff really that hard?
No one forces Russia to attack its neighbors.
As long as Russia insists on waging war against its sovereign neighbors, Russia is a threat to Europe.