1

No, it turned out the debris wasn't from the plane.

I think the most amazing thing is that no one has claimed responsibility. Usually in things like this someone claims proudly to have done it.

2 I don't know what's up with that responsibility thing. In Russia they never claim responsibility, because if you do, you'll die much sooner than your might otherwise.

3 In Russia they didn't really need to, because everyone always knew it was Chechens.

4

In the Levant, though, it might be ISIS, or the Muslim Brotherhood, or the PLO, or Hamas, or Hezbollah, or some new group trying to make a name for itself. So since one purpose of terrorist attacks for groups like this is to gain prestige, recruits, and contributions, they always want to make sure people know who did it. Sometimes it has led to multiple groups pretending they were responsible even when they were not.

No one is taking credit for this one, which makes me wonder: is it a political shakedown? The Muslim Brotherhood, in particular, may be trying to get concessions from the Egyptian government in secret. Their threat would be to destroy the country's economy by chasing all the tourists away, and maybe this bombing was to prove that they can do it.

Tourism is about half the economy and a major source of foreign currency but it's very fragile. If tourists believe they'll die if they try to visit, there are lots of other places they could go instead which are far safer, like Greece. The economy of Greece may be a basket case, but no one is blowing up tourists there.

Once Egypt has a reputation as being a dangerous place, it'll be really hard to get the tourists to come back.

5 Egypt's tourism hasn't recovered from the coup.
The interesting question is the passenger manifest.  There's a lot of "good" reasons for a terrorist group to assassinate someone by blowing up an airplane.  It's sad that it's happened, but it's the nature of the world right now.