Who is to blame for the Ukraine crisis?

Ultimately Ukraine may be forced to accede to Russian demands. It could become a satellite state, rather than a democracy, the impact of which would be felt across Europe. This is solely because Western powers dumped a democratic nation. Also, does Putin have an end game or would he be bogged down as in Afghanistan? Would Russia have acted similarly had Ukraine held on to its nuclear weapons rather than surrender them on Western guarantees in 1991?