MRSA is just a version of staph aureus that is resistant to some common antibiotics. The antibiotic resistant version is common everywhere now since we use so much antibiotics. The antibiotic resistant version doesn’t make someone sicker in and of itself than the non resistant version, it just doesn’t respond to some antibiotics. From context I gather this was MRSA pneumonia.
Staph aureus lives on all of our skin, mouth and external surfaces. It’s not like something you catch, it’s something that’s already there and takes advantage of an opening, like a wound, lungs already damaged by a recent flu virus or something, or a weakened immune system. It’s common that people in the hospital get staph infections, because they’re already there for something else making them sick that gives staph an opening. Strokes are also more common in hospitalized patients that are sick with other things. Strokes usually aren’t directly related to an infection, but the pro inflammatory response can increase clotting and make a stroke more likely. Strokes also can inversely make pneumonia more likely, if you have trouble swallowing and saliva and secretions are going down the wrong tube, then it creates an easy way for bacteria from your mouth like staph to get to the lungs and start up a pneumonia.
Tldr: MRSA is on your skin right now, don’t worry about it too much, don’t overuse antibiotics