Lots of questions, here, but the easiest ones first: in general (as noted, the political spectrum in Israel is very diverse and vociferous, so it’s easy to find exceptions) the Israeli populace considers this a good thing, long delayed for what are seen as silly or unfair reasons.
First off, Jerusalem IS Israel’s capital. Ignoring the very long history of being our capital just to avoid the history lesson, the entire apparatus of Israel’s government is in Jerusalem --prime minister’s office, the bureaucracy and all that comes with the executive branch, Knesset (i.e., our Congress), the supreme court, etc. Everything is there, and has been since ~1949. This is not a new thing.
Every other country in the world picks its capital; it’s logical, and no one cares. Except with Israel.
Well, why the double standard?, we ask.
The reason is, of course, is the separatist Arabs in the PA (to be distinguished from the Israeli Arabs in Israel and Arabs in Jordan and Egypt) not only want Jerusalem to be their capital – but they want Jerusalem to be EXCLUSIVELY their capital. No Jews allowed.
The official Israeli position is we are happy to share (again, there are plenty of divisive voices on this end, too).
Now, the position that Jews-can’t-live-in-Jerusalem is pretty silly.
And the PA’s claim that they want Jerusalem to be their capital is really not practical, in that the PA’s seat of government is in Ramallah (a historically Christian city until it was ethnically “cleansed” of troublesome Christians, which is another dispute), but, hey if they want to move their entire apparatus of government to Jerusalem, so be it.
Most importantly, it is common knowledge that the separatist Arabs don’t give a crap about this. They don’t want to give up a bargaining chip. (And they don’t like Jews, so anything that they can do to cause grief is good.)
In short, it’s like a 1970’s style business negotiation (taught in business school) where a side throws up a bunch of meaningless roadblocks to get what they really want, in order to trade away stuff they don’t care about and keep what they care about. This was one of the meaningless chips.
So, Trump (who also read those 1970s business books) knocked off a silly chip off the bargaining table to knock things off center.
The don’t-upset-the-Arabs approach hasn’t worked since 1949, so he’ll upset them. So they riot. If it’s Tuesday, they riot.
Regarding the practicalities, I believe Israel gave the USA the land and the USA built a “consulate” that is bigger than the “embassy” in Tel Aviv, so, while there will be much porting of computers and moving of CIA agents, and the US Ambassador (who already spends most of his time in Jerusalem given the government is there) gets a new plaque on the wall.
It’s just not that big of a deal, logistically.
It’s a big symbolic move for Israel that the nations of the world stop holding us to a double standard, especially one so silly.