Joey jojo, I will answer to the best of my ability. Not an easy subject to put in lay terms. Let me know if you are unclear of something or don't understand what I am saying.
To start off with, the COVID vaccines are not vaccines but gene therapy. The definition in dictionaries has been changed recently, if you want to look it up.
In the olden days vaccines worked on the basis of attenuating a bacterium or virus by inactivating it or killing it. The attenuated virus/bacterium or parts of it is injected into a person. His/her immune system is trained by these to recognize and react to the real thing. The RNA vaccines do not work on this basis at all. You can look it up.
When a person encounter the virus, his/her immune system manufactures antibodies. These control the virus and eventually kill it. Now when injecting this person with the COVID vaccine, causing his cells to manufacture spike proteins, of course his immune system is going to react by instituting an immune response. A person that has never come in contact with the virus, will manufacture antibodies against the spike proteins in order to recognize the real thing and act against it. (By the way, the spike protein of the variants have mutated to such an extent that it is virtually a new virus and unrecognizable by the immune response of a vaccinated person, thus the so-called "breakthrough infections" found in vaccinated people.)
But the immune system of a person that had previous contact with the virus is also going to react. Problem is, his cells are now producing spike protein with the help of the vaccine. His primed immune system will immediately start attacking these cells producing spike protein, thus the damage to arteries and veins, causing blood clots, and attacking heart muscle, etc. Remember all your cells are now producing spike protein.
Here's an article on the danger of vaccines, especially COVID vaccines. It goes into ADE (Antibody-dependent Infection Enhancement). This is something that did occur in past vaccines where the vaccine killed more people than the illness. Now Coronavirus vaccines are especially prone to this: