You think they failed, but everything in the Bible will come true. The prophecy that the mark of the beast will be used to pay for things. People today are figuring out how to pay for things with marks. And someone will use 666.
And Nebuchadnezzar did take over Egypt.
Exodus 21:16 says, “Whoever steals a man and sells him, and anyone found in possession of him, shall be put to death.” That's basically what happened if you had a slave.
Effectively, Israelite slaves could break their service contracts simply by leaving. Slavery in Israelite law was entered into voluntarily and could be ended voluntarily.