I'm glad you asked.
First, any of us who are not anti vaxxers (I am not anti vax) would have gladly welcomed Pfizer and others making a vaccine against Covid. That is not an issue.
However, as evidence comes out that Covid was a virus made in a bioweapons lab and was an act of war (Trump had some idea of this but more evidence has come out since) and since evidence has come out that Fauci funded this research, lied about, and tried to hide this fact all while undermining President Trump (probably something that Trump was not aware of or at least not fully aware of) and since we now know that Fauci cheered those governors who caused the greatest number of deaths (Cuomo, etc) all while lying about the efficacy of HCQ which probably killed tens of thousands of Americans. These are things that we know now that Trump either didn't know or didn't fully know and would make any competent thinking person question what is going on.
Not only so this took place during the height of his campaign for reelection which must have consumed a lot of his time and distracted him whereas we have had 12 months to carefully peruse the information.
Still, Trump was no longer in office when the vast majority of Americans were vaccinated. All of my concerns about this vaccine are a result of doctors raising alarms from what they are seeing, observations that have all taken place after Trump left office.