At Samar, the DDs, DEs, and aircraft from the Taffys all combined to disrupt Kurita's attack. Every time a DD, DE, or Avenger fired torpedoes, the targeted ship(s) had to turn to evade, keeping that course for the several minutes of the torpedo run(s). An Avenger making a fake run - which did happen - still forced IJN ships to evade. The planes of Taffy 3 attacked with whatever they had, but after some time, appropriately armed planes from Taffy 2 and Taffy 1 and rearmed Taff 3 planes joined the attack. The DDs' and DEs' attacks and sacrifice were heroic and beyond, but air attacks also did damage and contributed to the chaos.
Keep in mind, too, that Kurita had had two ships sunk out from under him, losing charts and plans, and some of his staff scattered by their being rescued by different ships. His decision-making capacity had to have been affected.
Japanese radar was a generation or two behind the USN's best. It was not adequate for gunnery direction. So Kurita's ships weren't going to lose track of Taffy 3, but their gunnery direction was optical and their directors had to recalculate and reset every time a targeted American ship ducked into a rain squall or made a sharp course change (which the DDs and DEs did). At some point Kurita realized that his force was being attacked by many more planes than could come from the task group he was attacking and they were likely to keep doing damage while he did not really know who or where those extra carriers were. He probably realized that the damage he might do would be far less than the the probable total destruction of his force and he decided to save his force for some hypothetical future, better, opportunity.
The Iowas' machinery is so antiquated that finding people who know how operate and maintain it would be extremely difficult at best. Replacement parts for the machinery would be unavailable. The electric generation capacity of the Iowas is not sufficient for modern electronics. The Iowas' propulsion and weapons machinery requires manual operation, which entails a large crew. The cumulative weapons power - Tomahawk missiles, the 16"/50 main guns (for which there are no stocks of shells), and the 5"/38 secondaries - are just not great enough for the cost of the crew and logistics necessary to operate the ships.
