It's been my experience that infantry officers are in general more professional, engaged, and intellectual than their navy counterparts. The expectations placed on those that will be leading men directly in harms way and getting out there in every clime and time are a little different than the ones for officers working regular shifts and living in a cabin on ship.
Which army or armies are you basing this comparison on? Obviously there are olnty of good professional armies where this is true.
However there are also a pretty large number of ‘police’ or ‘ceremonial’ armies, or just corrupt ones or poorly funded many of which haven’t seen real combat in decades, or perhaps ever since their country came to be. These ones often develop/decay into complete combat unreadiness.
The current bundeswher or the US army between the world wars are good examples of how dramatic underfunding in peacetime can leave a military hopelessly incapable. Recruits drilling with broomsticks who have only fired a few rounds in training to save on ammunition costs; 1 in 5 or 1 in 10 aircraft combat ready; critical shortages of spares and munitions; heavy equipment like tanks decrepit or never even ordered; the list goes on. Most of the force is people killing time and drawing a check for a little while before moving on to something else.