Vol 2 crashed Netflix servers for about 30 minutes when it dropped.
You can kiss the days of all episodes dropping at once goodbye. Splitting seasons up makes way more sense for these networks.
Word of mouth has a chance to spread, new hype every week/month instead of for just 1 week, etc.
AMC did it first with Walking Dead
This is what worked for cable for decades.
However, streaming services initially wanted to be different from cable and bring in viewers through "instant gratification".
Now, more streaming services are doing weekly or monthly releases of episodes.