*Influence in the workplace for her career
Money, gifts, sugar daddy type role
The ego boost of having someone desperate for her attention that she can control
The power trip of "stealing" someone from wife/family
I'm not saying any of these apply to this particular young woman but I have seen similar situations for all of the above. None of them ended well.
Be wary.*
There are also rather ordinary reasons; (some).young men might tend to see older women as milfs, cougers etc and fairly game for casual, sexual relationships, but nor commonly for "real" relationships. Women don't tend to ge so "ageist" re potential partners, and may consider up to 40s as potential relationship material. This is also facilitated by the fact they could have kids with them later (not anywhere near so feasible with older women).
So saying a uoung woman wouldn't be interested in a (real) relationship with a man in eg mid 40s (esp if he's a decent looking mid 40s) is a fallacy. Some young women would be.
The (apparent) maturity and experience and seniority is also a plus point.
Added to that, that the older men appear to be more settled , with more assets because they're further up the ladder, career wise, housing wise etc (young women can be naive about the fact that that's in part due to his partner's labour, whether outside or inside the home, and naive about whether he'll after a split, though let's face it, a lot of men are better off after a split than their exes) ...... it's amazing (horrifying) how many think his wife is a parasitic appendage who'll conveniently bugger off on divorce and then resend her having a penny of child support).
In short; it's unrealistic to think 20s women are not interested in relationships with 40s men; if theyre reasonably attractive, they could well be. And they may not realise the age gap issues until well into a relationship.