Hyperion, simple and quick answer.

Long answer is more boring, Hyperion is a roblox "anti-tamper" software. Meaning it detects software e.g JJsploit, realises it's not supposed to be there, quickly bans the user, or warns, or whatever roblox ban message.

This in also support of recent revelations in roblox anti-cheat (e.g banning alt accounts) have made it harder. 

But you are cheating, and you did get banned. Which is only fair considering you did break roblox TOS. Don't cheat if you aren't ready to get banned in my words.

If you followed the instructions for the original prior JJsploit downloads, then you could've completely missed this part.

Windows defender detects any executor, regardless of creator as a trojan. Since the executor is supposed to inject into a game using code that defender is uneasy about and does a false flag

It's probably only happening now because:

A: you knew what you were doing since you watched the tutorial before, but now forgot a component
B: There may have been a defender update, or something along those lines (yap yap yap, very unlikely it's this)

Either way, this isn't a worry, just a false flag. 

Few questions:
1. How long are you getting banned for? 
2. is it spread across accounts?

3. How long usually until you get banned from JJsploit?

And yeah, if you're using JJSploit you are likely to get banned, because you're cheating and broke roblox's TOS. This is the same for other executors. You knew the consequences.

You can't necessarily avoid getting banned, minimise it for sure, personal opinion is to use JJ in interludes rather then big sessions perchance, haven't tried it myself but it may reduce the chance. Not by very much though. Very likely you're going to get banned either way.