What creates El Niño and La Niña?

What are the reasons behind the fact that the currents in the Pacific ocean are oscillating/changing at irregular intervals? Is it the changes in the strength of the dominant/most common air currents, water currents or has the Earth's rotation a big impact?

Some climate scientists have linked the past twenty years, more frequent and stronger El Niños with the air current changes due to global warming of the atmosphere. With a warmer atmosphere the relative power/speed of the rising hot air from the earth/oceans becomes weaker. Winds would then be weaker and reduce the drive of the water flow westwards

If it is an imbalance in the water system, which leads to El Niño, it is more difficult to find a connection to the global warming of the atmosphere. It is the sun that warms the ocean surface and if the warming shifts/oscillates, it would rather be due to changes in solar radiation intensity? El Niño would then be created because the amount of warm water in the west is too big, "the water mountain will be too high" and would begin to drift eastward physically.

Is it the rotation of the earth that creates the changes in ocean currents the picture becomes yet another. It is the rotation that together with the trade winds keep the hill of warm surface water to prevent it from sliding to the east. The so-called Coriolis power is an effect of Earth's rotation, and is according to researchers the power that prevents the giant sea mountain, created by the trade winds, to move eastwards. The difference of the height on the “warm water mountain” is as much as 45 cm, compared to normal sea level, but the volume is huge.