I really think governments have better things to be doing with their time than worrying about a problem (the certification of deep sea submersibles) that has cost 5 lives this year. Maybe this decade. Maybe this century, I dunno.
To put that into some kind of perspective, there were 1,695 road fatalities in the UK alone in 2022. That's just under 5 a day. Roughly the same. One highly newsworthy incident does not mean that Something Must Be Done.
An expensive sub failed and some people were killed. Very sad. But not a cause for any policy change. Maybe when they are being lost at the rate of one a week or one a day ... then it will get to compete with other things in the Something Must Be Done queue.