I will answer several side questions to light up yours. I tried to mainly focus on the special features of your scenario (sudden rise in intelligence and newborns being normal).
Does the capacity to be a powerful villain increase faster than the capacity to prevent criminal actions, when intelligence rises ?
There is no answer to this question, but it has to be considered.
You can argue that it is easier to drop a bomb in an hospital than to prevent it, for example, and conclude that villains will become proportionally more efficient than good guys, due to the increase in intelligence.
You can argue the other way around as well. For example by saying that since good guys are more numerous, the total gain in intelligence is way greater than for villains.
Therefore, the increase in overall intelligence could be more destructive than constructive, just due to that effect.
Will people mentally support their new intelligence ?
I have not an IQ of 300, but if tomorrow I suddenly do, this will radically change my view of the world. I will perhaps think that I wasted most of my life in futilities and probably conclude that I used to suck at tactical games. Taking this in consideration, it is possible that a non-negligible portion of the population turn mad.
Will IQ of 300 severely injure children development ?
Children do not have high IQ (in comparison with adults), in fact most of the cognitive capabilities come quite late (capacity for abstract thinking comes usually during adolescence, 12-16 ans according to Piaget). How will high cognitives capacities injure the capacities of children to acquire other abilities normally learnt during childhood, such as social behaviour ?
That could turn really bad. Especially when combined with the following part :
How will the terrible generation gap be managed ?
Since newborns after the event of massive geniuses making will not be geniuses, it can causes several problems. For the people having experienced normal IQ, compassion could smooth every thing, since they remember being normal. But for the young, it will be hard to understand how can somebody be so stupid. Of course, they are geniuses, they will be able to figure it out, but will they have the patience to deal with such stupid people ? And if they do, how ?
Of course they may want to make them geniuses as well, that would be a good scenario.
But they could also conclude that prolonging their own life is a way better investment than turning normal people into geniuses.
How will the elites cope with the sudden equality of all ?
Since everybody get the exact same intelligence in your scenario, how will our current society, which rewards people based on abilities, deal with everybody becoming totally equal suddenly ?
Maybe people will consider being smart enough to govern themselves, without the need of a proper government. People previously in charge could react quite violently against that.
Appendix : on the implications of high IQ
(part added following a discussion in the comments)
An important thing has to be noted : no strict implication can be proven between high IQ and any other mental ability. The reason is that you can not manipulate a person IQ, therefore you can not experiment and draw conclusion.
However, strong correlations have been established, for example relating high IQ to high job performance. But correlation does not mean implication, it might be that a third factor is the root of both high IQ and high performances.
For example, it is not clear that high IQ implies high imagination. It might be correlated, and it even might be that imagination implies high IQ (since imagining things is a mental exercise, it would be a valid theory).
Therefore my whole answer is based on the fact that you can not predict clearly the effect of the IQ surge. Will that make people more open minded ? Will that make people reconsidering their old views ? In the context of worldbuilding you need to ask yourself the question but no answer can be dismissed as incoherent.
We may argue that yes it will, and this point of view is totally legit. Geniuses tend to be open minded, open to criticisms and imaginative. But if we do not explicitly include them in your definition of "genius", your "geniuses" are not assure to have this traits. Conditioning have been proven powerful (see Milgram experiment or the third wave), should not be underestimate (for example when talking about soldiers loyalty to government) and we do not know if rise in IQ (or any form off intelligence) would make people aware of it and/or capable of overcoming it.
Genius can have irrational behaviour, a traumatic example is known in science. When quantum physics was build, Einstein (widely recognize as a genius) refuse to accept part of the theory, because he strongly believed in a deterministic universe (he was quoted to say "God does not play with dice"), when the theory was based on a non deterministic universe.
His beliefs make him refuse a scientific theory. Anybody can spot that he was wrong to refuse the theory for this reason, but he did, and this show us that geniuses can have opinions fully based on unverified beliefs.