I'm tempted to lock this for sensationalism. The top of four layers of cockpit glass cracked. While it's SOP to return to port after detecting a crack in the cockpit, this type of damage isn't uncommon in Boeing aircraft, including the 787:
I mean, it's not great to have planes be forced to turn around because of cracked glass and I think this is the first 737 to experience the issue, but it's not a big deal imo.
Stress is eventually going to cause wear and then failure to lots of parts, especially ones on the outermost layer of the plane. That's why they're over-engineered. Does there need to be 4 layers of cockpit windshield? Probably not, but humans make mistakes and we're lucky to have those extra layers so we can turn around and land safely.
This sounds like the phenomenon where any tiny unrelated issue with a plane is scrutinized by the media after an accident, even if these minor issues are common. I have no idea if this issue is serious, but I wouldn't assume it is until we get more info.
A crack formed on the outermost of 4 layers. It's within spec but should've been caught on inspection. This is a bad look for ANA's inspection team (which might be Boeing? I'm not sure), but not a manufacturing defect afaik.