That's what all viruses do, mutate rapidly. SARS-CoV-2 is no different. But it can't mutate unless it's reproducing. This requires infecting more people. As more people get infected, more virus reproductions occur, and more mutations accumulate. This is why virologists, infectious disease physicians, and all scientists, have been screaming for people to roll up their sleeves and get the jab. The best way to stop this pandemic is to vaccinate at least 80 to 90% of all people on the planet.
The alternative is to wait until everyone on earth has been infected by the virus. This will take many years. An estimated 0.5% to 5% of the world's population could die. Presently, the world's population is estimated to be 79 billion people. That becomes 0.4 to 4 billion deaths. And that's only if no more successful mutations occur.