Because, Ladybj, if blood clotting was a side effect of this vaccine, it would be widely known by known by now, and would be shouted from the rooftops. Your mention of your husband's health problems is the first I (or probably anyone else) has heard of a connection to the vaccine. You might as well say he had such-and-such for breakfast, and that's what caused the blood clots.
And all kinds of health problems can cause blood clots. One is a-fib (atrial fibrillation), which he may have, as it's very common. It can cause serious blood clots which cause strokes. That's why I (and half the people I know) are taking Eliquis, a blood thinner.
Blaming everything that comes along on the vaccine is just plain ridiculous. But those who have been conditioned to think that way for some political reason will desperately reach out to find anything, no matter how farfetched, to blame on it. I'mnot saying that you are one of those people, but you are providing them with ammunition to use against this lifesaving vaccine.
What "research" are you planning to do? Reading all the stuff on the Internet about it? That isn't research. If you do come up with some legitimate, scientific proof that the vaccine causes blood clots, please quote your source of information.