The real spike proteins are insoluble and stick to certain membranes, like in your lungs. The mutant ones are shorter and more soluble, so they can more easily

The real spike proteins are insoluble and stick to certain membranes, like in your lungs. The mutant ones are shorter and more soluble, so they can more easily accumulate elsewhere, e.g. the blood vessels in your brain: hence the vaccine-induced brain blood clots.