Even the smaller competitors like Bombardier would have an interest in this, even if they are not the manufacturers of similar sized aircraft, a loss of faith in the aviation industry hurts everyone too. Plus suppliers etc.
As for the investigators (I know you meant FAA, not FCC), we have a similar issue in medical devices - you need seriously well educated experts to perform the investigations, and it is hard to find any without industry experience which wouldn’t look good on paper. The solution is to try as hard as you can to not have ex-employees audit their ex-bosses, but it isn’t always possible so we accept some overlap. It doesn’t mean these people don’t take their job seriously.
You need an incredibly robust quality management system to even achieve certification (allowing you to place on the market) when creating systems which include life support function, or functions which potentially could kill a user. All potential changes both within and outside of the manufacturers’ control MUST be assessed and constantly monitored so such issues CANNOT arise.
No one should be able to legally place an unsafe app on the market, or legally perform changes to the app without the necessary checks and balances.
Medical device approvals in most countries are definitely not the wild west. Although they are not perfect.