What’s new is that the main stations (as opposed to the secondary stations like KTVU-Plus) will add a 30-minute live newscast at 11:30 PM, immediately following their 11 PM newscast. Presumably, that would mean newscasts at 10:30 for stations in the Central/Mountain time zones.
In many markets that will mean a 2-hour late news block–and potentially, a 2-hour repeat on one of their stations in the middle of the night.
There are two other reasons: They are called the 2018 Midterm Elections and the 2020 Presidential Election.
Candidates, parties, and (especially) outside groups will spend a record amount of money for a midterm election on TV spots, and may also break a record for TV ad spending in any election year in 2020.
Political advertisers usually prefer to place spots on news programs than entertainment shows.
Additionally, many local stations (except in smaller markets) can expand local news without incurring much in the way of additional expenses. In many cases, the expanded airtime will be almost 100% profit, since more money will come from the additional commercial spots while the expenses for such expanded newscasts often don’t rise much at all.