Without lockdown he would have been active- that was his job that he was prevented from doing because of the lockdown. There may well be somè underlying factor, but the lockdown caused him to be unable to live his usual lifestyle which had health benefirs.
There is a world of difference between a fitness trainer being less active than usual due to lockdown, and being so sedentary whilst gaming that he developed DVT. He might have been prevented from doing his job, but he wasn’t forced to remain completely immobile. Lockdown doesn’t require anyone to give up all physical movement.
I have an entirely sedentary job which means that during busy periods I sit in front of the computer for hours on end. I still make the effort to walk, cycle, do yoga, etc., because I understand that it’s essential to my health, even though fitness is not my profession.
It’s shabby reporting: the media are running out of hyperbolic scaremongering stories so they’re clutching at straws. Any untimely death can and will be spun as a click-bait lockdown/COVID tragedy.