There are 40,000,000 people in the US over 65
Over 20,000,000 of those are now vaccinated in the last three months.
540,000 Americans over 65 will pass over that 3 month period = 90 days
6000 a day. 3000 will have been vaccinated (minimum)
The odds that it would be on the specific day of their vaccination would again be 1 out of 90 and be 33 per day or 330 would die within 10 days of their vaccination.
Since these are 2018 numbers, they were pre-COVID so COVID had no influence. It is just pure chance. Roll of the dice.
The only real influence on the numbers would be human.
What you are calling spectacular is actually not spectacular at all. It is normal. It would happen if you shot saline solution in their arms.