They were expelled because they started a war, Israel accepted the partition whereas pals did not. Israel was explicit they did not want to displace anyone. Many arabs live in Israel to this day. If there was no war there would have been no expulsion.
Pals have been offered states numerous times and even offered right of return for some refugees with compensation to the rest.
And even though you did not answer my question I will answer yours- no I do not think the arabs who were forced out in a war and who have been fighting a war since then should be allowed back en masse when they openly say they wish to destroy Israel. And if you want to re visit past injustices to say there are some arabs who should return, have land given back, then you also need to consider the Jews which were kicked out of the west bank like from Hebron and the Jews which were kicked out of Arab countries and of course the Jews which were kicked out of Europe. If you launch a war, lose , you can’t ask for a do ever where you get everything back and keep everything you took, it is ridiculous. At the outset the Jews were willing to accept a tiny state, that they were fleeing from the Holocaust, that Jews were living in refugee camps until 1948 when Israel was established. That Jews are the natives of the land, were making it prosperous, are integral to the history, and the arabs sided with the Nazis in WW2. They are truly disgusting, is it really so horrible to live around Jews , in their native land. You think the fact the pals had to move 50 miles down the road is some horrible injustice ?
From the start of the conflict and throughout the modern era Israel has always been willing to live in peace with the pals despite their belligerence making numerous offers. Jews never asked for welfare like the Muslim immigrants coming to Europe, they developed the land and caused many arabs to come. It is the pals who have belligerent, following fundamentalist islam saying there can be no Jewish state, everywhere has to be a Muslim state.