I'd add the move from feature phones to smart phones and later tablets. Early adopters were getting them 2007/08, 5 years on from that the platform was well on its way to maturing and with a broader range of hardware and the software ecosystem was moving to target it too. Then there's the question of what form best suits the usage the tasks the netbook audience have, if you're doing the very basic browsing/comms tasks, why take a comparatively big slab when a 4-5" will do, and if you do need a portable PC why constrain yourself to a weak system, netbooks were in no-mans-land.
perhaps, but chromebooks still come in laptop sizes these days. Other than a few stragglers (e.g lenovo duet), the majority of chromebooks are 12-14 inches.
If you are chasing the form factor, macbooks are serious competitors with really good battery life and tactile feel.
The beauty of netbooks was that ~10 inch form factor. Really the perfect companion device without needing a special bag to carry.
In many ways netbooks were a over a decade too early, and came right before the mobile hardware computing boom.
Netbooks are still not feasibile today, modern web design has made smaller lower res displays completely unusable today.
Tech Companies are trying to push foldable phones and tablets into this niche - but there was always something nice about a keyboard.