I think my question is different from this.
Some movies' productions release Blu-ray/DVD so early after theatrical release, others will take time. How do they decide for the Blu-ray/DVD release date?
This is a regional thing. In the UK it's normally 17 weeks by agreement with cinemas. Famously in 2010 they upset the cinemas by trying a 14 week window to avoid a clash with the World Cup:
In early 2010, Disney announced it would be putting out the DVD and Blu-ray versions of Tim Burton's Alice in Wonderland 14 weeks after the movie's release date (instead of the usual 17) in order to avoid competition from the 2010 World Cup. In response to such statements, theater owners made threats not to show the movie on their screens, but later reconsidered their position before the movie was released.