I imagine it was added to mark the unfortunate man as an accomplished, educated member of society. It is done to add a grander sense of loss to society in the story - the same way they include his family status and the fact that he was clutching his little girls teddy to let the reader empathize.
I imagine they add the brexit lawyer part to make him seem like he is doing something the mail and its readers deem noteworthy or positive. The whole story is also written inferring that his death is a direct result of these complaints to match the narrative the DM and its readers love to add when talking about men behaving inappropriately towards women.
The Guardian could have gone the complete other way and painted a different story of a 'have it all' lawyer currently taking advantage of brexit to make money behaving inappropriate to female colleagues before selfishly taking his life because he is afraid his reputation will be ruined.
"A Brexit lawyer tasked with helping businesses make a success of Brexit has instead been spending his time drinking to excess and sexually abusing his coworkers according to allegations made this week. Mr Lawyers body was found earlier this week following his apparent suicide, scuppering any hopes of a meaningful investigation into his conduct."
Something along those lines? The thing is the Daily Mails audience seem to lap this stuff up regardless of how it's framed. The key word in what I've written above is allegation, it's the only one that's not designed to inflame opinion, and it needs to be included to avoid potential libel prosecutions, it's also the only one that will be roundly ignored by the readers. The only information we have in the main report that is of any relevance is that some allegations had been made.
The Guardian has its own bias but it's not even in the same league as the Mail, they've turned population stoking into an art form.
It does make me worry for society in general.