the_emi_guy said:
Specifically, when the quark theory was confirmed with the discovery of the omega minus particle in 1964, particles containing up,down, and strange had been observed. Looking at table of particles (various sources), I see only 26 hadrons that contain these three quarks, 15 baryons and 11 mesons. Even if we double this to include anti-particles it seems way short of the "zoo".
Part of what made it a "zoo" is that new hadrons kept being discovered at a rapid pace and nobody had any idea how many hadrons were out there to be discovered or how to categorize the ones that were discovered in a physically meaningful way. They didn't even know really, if hadrons with similar properties (e.g. spin, charge, parity, mass) were all one kind of hadron, or had subtypes discernible by some unknown means. The lack of order or sense in what was already discovered and what continued to be discovered at a rapid pace, contributed to the feeling that it was a "zoo".
Also, while you state that "quark theory was confirmed . . . in 1964", the entire scientific establishment doesn't just adopt a new theory instantaneously when a single experiment providing empirical evidence for it reports a result. A discovery like this may win over lots of people, especially those at the cutting edge of research, quickly, but it takes something like a decade for a discovery like that to be fully assimilated into the physics community to the point that it becomes scientific consensus (and a few die hards will inevitably cling to their own, since disproven pet theories with epicycle-like fixes, until they die).
For example, there are still people today who cling to Technicolor theories (which were designed to provide an alternative explanation for phenomena attributable to the Higgs boson in the Standard Model, in the event that no Higgs boson was discovered) despite the discovery of the Higgs boson.
Plenty of people of good will are going to doubt a particular experimental result until it has been robustly and precisely confirmed by multiple experiments using more than one methodology. Quark theory wasn't almost universally agreed to be correct until the very late 1960s or early 1970s, even though it was gaining converts very rapidly in that time period.
This is especially true across sub-disciplinary lines. Sub-disciplines adopt discoveries from other sub-disciplines investigating the same thing more slowly than those in the sub-discipline where the original discovery is made. For example, I see papers every month from HEP physicists at arXiv proposing dark matter candidates that haven't been ruled out using HEP methods even though astronomy data already rules out these candidates, without any mention (and probably without any knowledge) of the relevant data from another field investigating the same thing using different methods. Back in the early 1960s, for example, bubble chamber researchers might not have been on the same page of collider researchers who may not have been on the same page as "nuclear physicists" that worked with nuclear power plants.