What caused them to be so radical that they saw kamikaze fighting as effective/viable form of attack. Did it have to do anything with the Bushido code? Where did their fanaticism come from?
You seem to be asking several questions here.
Japanese troops fought to the death more because of several reasons, a significant one being the refusal of Allied troops to take prisoners or desecrating war dead, for instance, by having war trophies in the form of skulls or fingers. After a few incidents where surrendered Japanese troops turned on their captors, taking prisoners became extremely rare among the allies until Allied intelligence promised enough incentive for them to do so. It was thought that racism may have been a factor as well in this regard.
As for why the kamikaze was used, it was partly due to the sheer decimation of the Japanese air corps. Most of their good pilots had been attritioned or killed in extremely brutal battles, and Japan had made it very difficult to become a naval aviation pilot in order to ensure they had the best of the best. This hurt them, however, as it prevented them from mobilizing a large trained pilot corps until it was too late to matter. As a result, kamikaze attacks were used as they were much easier to train-rather than train a pilot on how to prepare a dive bombing or torpedo attack run, it was a matter of orienting the plane from point A to point B.
As to why they were motivated such, it partly had to do with the strict hierarchy of the Japanese military, and partly had to do with desperation. Tameichi Hara wrote how
"He told me how he told (prospective kamikaze pilots) tales of how pilots with hundreds of hours of flying experience were shot down like flies in the Solomons... they volunteered."
For all these pilots knew, this was a battle for Japan's existence, to defend their family and friends from a threat that would destroy everything that they held dear. It was something that Japan's best had died for. If they died but were able to save their family by doing so, they saw that as worth it.
As for the hierarchical bit, Tameichi Hara writes during the navy's planning for Operation Ten-Go, the final sortie of the Battleship Yamato, how despite every single captain arguing against the mission on the grounds that it was suicidal and a waste of lives, when the decision finally came down, they all acquiesced. And that the most extraordinary act that they had done was when he decided that they had brought too many days of food and supplies with them (as it was going to be a one-way trip), and how he had given it back to the quartermaster because they would not need it. Its quite surreal.