Sorry to keep you waiting for the answer. I was trying to identify the thief through Huobi, cause the transaction finally ended at 1L5tLc6ayc3RXAyicHRv2c2uSNVJzoP4Yp Huobi account, that probably accumulates multiple other thefts.
No problem, it would be really great if something could be done from Huobi, they can freeze that address and conduct an investigation, so there would be hope for a refund of stolen coins.
Regarding everything else in your case, you can never be completely sure that the failure did not come from you, but this does not mean that the fault cannot be on the other side. The problem is in proving that blockchain.com is have some security glitch, I doubt they would ever admit it.
Did you see this thread?
https://bitcointalk.org/index.php?topic=5157460.0Users who are convinced they lost 400 Bitcoins due to some vulnerability had a plan to sue blockchain.com (ex info), you can contact them for more info.