To say that theoretical physics has been ahead of experimental physics from 1905 onwards is not entirely accurate. In the 1960s particle accelerators had found

To say that theoretical physics has been ahead of experimental physics from 1905 onwards is not entirely accurate. In the 1960s particle accelerators had found lots of particles. At first those were thought to be elementary, but more and more were found, into the hundreds. Physicists started doubting that they were elementary. The quark model eventually explained that those hundreds of particles aren't elementary. Saying that theory is ahead of experiment also suffers from survivorship bias. We tend to forget the theoretical predictions that didn't pan out. If the theoretical side predicts 10 different possibilities and the experiments eventually find that one of those is right, that's not evidence that theory is ahead of experiment. We also tend to interpret correct theoretical predictions in a more rosy light after the fact. One of the poster childs for theoretical predictions is the positron. It is said that Dirac predicted the positron, which is true. He first considered that an electron could be in a positive and negative state, but retracted that position later and said that the positive charges were holes in an infinite negative sea, and he theorised that the proton is a negative electron. He was eventually convinced by Oppenheimer that the infinite negative sea idea didn't make sense, and that's when he predicted that there was a positron particle in 1931. But the positron had already been observed two years earlier, although those observations weren't conclusive and the conclusive experiment was done in 1932. The interplay between theory and experiment is often nuanced.