Or maybe Ronin network just messed up and gave away their private keys to the hackers otherwise if this was possible, Don't you think so many addresses holding large amounts of Bitcoin would have been hacked by now?
Yes I do agree with this, I do believe that what happened to ronin network is insider job. and I know quantum computer capable doing lot of thing but what you have said is true
reuse-ing address is fine for daily transaction with account not more thang 1000$ as long you don't fall to scammer and hiding away your private key, but for privacy process using Wasabi wallet or other mixer is always be a great choice