Not sure if everyone agrees with the “100%” prohibited bit. I’ve heard claims by scholars Rig Veda does talk of beef being consumed, though others say its figurative language that has been misinterpreted!
From my 45 year study of Puranas and other associated Vedic texts, cow flesh was always totally prohibited. Doesn’t mean people never ate it, but it was utterly condemned. Cow is considered mother - gives milk, bull father - pulls plow and helps produce grains. Never to be killed. There were some animal sacrifices in which animals were killed, it was a mystic performance and not common for large animals to be sacrificed, for kings pretty much only. Basically the only flesh acceptable was game. Worshipers of Kali ate and do eat offerings to Kali, but it is usually done very irregularly. And even then, a mantra has to be recited into the goat’s ear (only can be goats) which roughly says “As I kill and eat you, in my next lifetime, so you will kill and eat me”. Once a month can be done, at a certain moon phase.
The number of Hindus who do not understand or follow the traditional texts is of course large, but thankfully there is a Hindu renaissance for some decades going on. Modi is really helping this, re-instituted reading Mahabharat and Ramayan in schools.