The police officers can only act on what they see. He could have had a histroy of police callouts but that did not mean they can come in and make demands from someone is in a care home for people whos brains do not function as "normal" and expect him to react in a "normal" way.
Most men dont react well to agressive demands and will meet aggression with aggression. This can be more of a problem with someone whos brain has forgotten learned socialisation. The police can be dealing with adult who react like a 2 year old in a strop but he did not even look/act highly agressive rather its as if he mirror the male officers reactions.
And while he may be acting out due to the lack of capacity, fustration or loss of control from being in a care home he was calm enough in the video but rather than trying to talk him into handing over the "knife" they went full Robocop
Did they check if he had a pacemaker or heart problems or asthma or copd?
The police like the rest of the emergency service deal with "frequent flyers" a lot from DV to drunks to mental health breakdowns.
Using the batten so soon after the pepperspray was overkill. Broken bones even broken skin can kill old people because their bodies dont have the repair capacity. If the officer had held back the ongoing chemical burn would have resulted in him looking for help.
And using a taser to immobilse him is "cheapskate" policing they had time to call in an extra team. Which they would have needed anyway if the plan was to remove him from the property.