Dunno, people that have been watching him for a decade or more have seen a significant change for the worse as of late. He was smart, shrewd, and in control. Not so much lately.
It may not be so ridiculous. If you watch his earlier public appearances - he's always a stone cold sociopath in control. In his latest appearances he's increasingly erratic and struggles to keep his cool. Remember he's 70 years old now which is well into the risk zone for serious health problems. Alzheimers? Terminal cancer? What would you do in his place if you were told that? What if he wants to go out with a bang? He couldn't just straight out declare war on NATO, what if by going after Ukraine he actually hopes for escalation?
Bonus : it feels like a true opportunity for someone powerful enough to steal the power.
Russia doesn't have enough manpower to conquer Europe and nukes are highly unlikely. The narrative that Putin is mad is ridiculous, he just decided that isolation from Europe is the lesser evil compared to being surrounded by NATO countries.
Nukes are highly unlikely because retaliation would damage everyone on all sides, Putin is just using them as leverage.
Once one side has technology to somehow defend from enemy nukes, then nukes could become a viable option, albeit an incredibly risky one.
This is just bluffs and media spreading fear.