Honestly, it could be or it could not be, most likely was not and you will never know. Grieve your loss, it is an awful loss and feeling and its clear you loved your father. Just be easy on yourself, you don't and will never really know what exactly in his condition caused his ultimate death. Transplants like this are risky period and complications can happen. It could have been the vax. Even with Covid overblown it sounds like he would have been the exact type to be at risk of death or certainly serious illness from it. Its awful to see loved ones like that, sad truth is most endings are very sad and not nice, it will be the reality of the majority of everyone. Most importantly a few moments at the end, even a few months of the end of one's life, do not matter. He had all the time before that created a family and loved and lived a life. When you remember him, think about what HE would want your to remember of him, the best parts and moments.
Honestly, it could be or it could not be, most likely was not and you will never know. Grieve your loss, it is an awful loss and feeling and its clear you loved your father. Just be easy on yourself, you don't and will never really know what exactly in his condition caused his ultimate death. Transplants like this are risky period and complications can happen. It could have been the vax. Even with Covid overblown it sounds like he would have been the exact type to be at risk of death or certainly serious illness from it. Its awful to see loved ones like that, sad truth is most endings are very sad and not nice, it will be the reality of the majority of everyone. Most importantly a few moments at the end, even a few months of the end of one's life, do not matter. He had all the time before that created a family and loved and lived a life. When you remember him, think about what HE would want your to remember of him, the best parts and moments.