HTS has changed a lot in 7 years. Back then they were essentially an al-Qaeda front group, but now they have explicitly separated from them and are more focused on Syrian national politics than religious theocracy.
Time will tell whether that holds up, and what Syria looks like is definitely a big unknown. But seven years ago HTS was quite different than it is now.
How does an organization make amends then? HTS has been governing Aleppo for some time now. They’re reaching out to groups they have been fighting to organize into a coalition. Even the former US ambassador to Syria has nice things to say about them. Whether HTS is a force for good or not remains to be seen - governing a country is different than rebelling obviously - but I don’t really agree with the premise of your statement. I think the way to absolve yourself is to do good works and to own your past.
From the US' POV, having Syria devolve into a theocracy is a small price to pay for the harm this inflicts on Russia (most notably losing their only port on the Mediterranean and forcing them to transit through the Hellespont, subject to the whims of Turkey)
Not really. Al-Assad was a known quantity and the relationship, while certainly not friendly, was at least stable (by Middle-Eastern standards). These guys on the other hand are an unknown, and that lack of predictability makes neighbours uneasy.