It may be many things, but I very much doubt the motivation is a money grab. A few people paying $45 isn't lining the pockets of some government official, or plugging a hole in any possible budget.
Dealing with the presence of travelers who haven't updated their driver's licenses requires a bunch of extra staff to perform the time-consuming additional verifications. The basic idea is for those staff to be paid by the people using them, rather than by taxpayers and air travelers more generally. As well as there being a small deterrent effect.
Is this the case, I didn't see it in the article.
If they have to perform extra work then I'd say it's justified. If it's just a punishment for not getting a real ID I'm not sure if that's fair
$45 x millions of people (some multiple times) = an incredibly consequential amount of money
There is no legal requirement to show id or answer any questions to establish identification before flying. In other words there is no extra work required by law which the fee would cover.