He did it to have the record of killing the world’s biggest lion and wanted to hang the head in his shrine. It was an arranged situation made possible with bribes.
Americans, in general, used to pride themselves in their exceptional achievements. It, and the competitive spirit which pushes it in any area of concentration, is fundamental to being American. It might be as relatively mundane as bowling a perfect game, or hitting a hole-in-one or a mid-court jump shot, or as exotic as a land speed record or rowing across the Atlantic. It is the way we are.
Socialism, incidentally, removes all such rewards for being the best, the brightest, the fastest, or strongest, and tries to 'equalize' people by ensuring no matter how well they do, they will get the same outcome as the person who couldn't be bothered but is capable enough they won't be shot for complete incompetence.
As far as the largest lion: that title goes to (according to the Guinness Book of Records) the heaviest lion ever weighed in the wild was a man-eater killed by Lennox Anderson in 1936, near Hectorspruit, Transvaal, South Africa, and weighed 313 kg. (686 pounds)
The heaviest male lion in captivity was a huge male named "Simba", which measured 320 cm. in total length and had a height of 112 cm. to the shoulders. Its weight was of 375 kg and died in 1973.
Cecil might have been photogenic and have had claims of popularity, but he was hardly the biggest.
As for arrangements, if there were illegal actions on the part of the dentist, guides, officials, or Professional Hunters, for whatever reason, they should be held responsible for their actions. If officials were bribed to look the other way, they should be held accountable, too.
That said, if the hunt was in fact legal, regardless of its popularity or lack thereof, the dogs of the media might be better employed shredding the Planned Parenthood people who are avoiding being prosecuted for selling the parts of babies aborted.
One lion is trifling compared to that slaughter.