Maybe it's because of the low cost of entry for competitors? If people get upset with what Facebook does to WhatsApp, many other services will spring up and people will migrate to them.
When it comes to thing like Internet service, it's not really the same situation.
Stage 1 - That doesn't make sense and will never work
Stage 2 - They turned down $1b they must be stupid
Stage 3 - It is a monopoly and needs to be stopped
Stages may vary but what remains the same is that nothing in tech is certain. Companies try really hard to create monopolies that will probably have anti-trust issues because the alternative is if they don't they will probably die (more so true after raising a lot of money and signing expensive long term office leases.)
From a longer historical perspective, nothing at all is certain. Take a look at the various office skyscrapers and stadiums in the US, the names change. Some of the giant corporations of 50 years ago may still be around in some form, but they are shadows of their former selves. The world changes fast.
When it comes to thing like Internet service, it's not really the same situation.