The problem with that theory is that it makes a base assumption that Putin is scared, acting now in fear of NATO expanding.
I don't think it takes a genius to work out why Putin doesn't want Ukraine in NATO and I think this compilation of an interview explains that pretty extensively.
https://x.com/nicholadrummond/status...88174843539935
It's almost beyond naive to think that if a statement was made saying 'Ukraine will never join NATO' that would have led to some happily ever after scenario where Ukraine remains a sovereign country.