Can you cite examples of requests for declaration of a disaster being rejected by a president? Such declarations happen so frequently, for many types of natural disasters.
Such declarations have happened for California wildfires, so it’s not a case of wildfires not qualifying as a federally defined natural disaster.
New Jersey was just denied Federal Assistance for extensive flooding damage last week. I worked for FEMA several years ago and I can tell you that many, many more state requests for assistance come in than are approved. I am not saying that politics did or didn’t play a part in the Texas decision (because honestly I don’t know) but it is not unheard of for a request to be denied. It actually was a pretty common occurance at one time and even within FEMA there were some who felt that the Federal government shouldn’t have gotten involved in as many disasters as they did.