Fitness isnt a brand she's just jumped on and you haven't been paying attention if you think so. She ran the marathon a little over a year ago and was training for that for more than 6+ months around her schedule. She even hired PT's to get her where she wanted to be. You don't just run a whole marathon for clout lol - You do it because you genuinely want too, she was raising awareness/money for a charity and theres no way I can criticise that. She was clearly very dedicated to it throughout the year.
I do think she was much healthier then, whereas now she is very much in the mindset of being part of the fitness community so is trying to assimilate to other accounts she sees as thats what will bring her in money/more followers. End of the day, I think she enjoys it. I think the logic behind this branding was "If I enjoy it, I may as well profit off it too" - Just like how Youtuber's started up in the first place.