1)
Why could no one else read the words?
1.
Metzudas David citing Sanhedrin 22a 1 : The letters were in three rows. The first row was Mem, Mem, Tov, Vov, Samech. The second row was Nun, Nun, Kuf, Pei, Yud. The third row was Aleph, Aleph, Lamed, Reish, Nun. They read each row, and could not understand. Daniel knew to read down, in columns. (The last word was formed from the last two columns.)
2.
Malbim (17): The forms of the letters were in a style that they did not know 2 .
