How can a stroke changes person's personality?

Yes. See the link below . There can be apathy, impulsiveness, depression and neglect of the affected side. What specific changes are you referring to? https://www.stroke.org/en/about-stroke/effects-of-stroke/emotional-effects-of-stroke/personality-changes-post-stroke

In many ways depending on the specific area of the brain affected by the stroke. From seizures to apathy or impulsivity, behavioral changes are to be expected. Talk to the neurologist involved about ways to address these symptoms.

Many stroke victims get depressed and others become highly frustrated by the outcomes. Speech therapy and occupational therapy have helped countless people