I get the point, but why a philologist at all to a planet with no intelligent life known to exist there?
Because it takes a long time and a great effort to get places in
Forbidden Planet compared to
Star Trek, and the implication of the twenty year gap before checking up on the Belleorphon party suggests that it was an even more arduous journey in Morbius's day. The humans in FP are very much conscious of the possibility of finding intelligent life (Adams and Ostrow discuss this directly in a scene cut from the final film), so it's reasonable that the UP would send a few specialists who would be important to a first contact along on a long-range scientific mission.
Note that the Bellerophon doesn't seem to have been a military craft like the C-57D - the only crew members specifically mentioned other than the captain were scientists, whereas the only apparent scientist on the C-57D
may be Ostrow.