Why did repeated "R" values occur in Bitcoin transactions before?
The R value is the result of EC point multiplication between the k value (known as the nonce) and the secp256k1 curve's generator point. It is effectively the public key for k. The only way that an R value can repeat is if k is also the same. Given that k is a 256 bit number and is supposed to be chosen completely randomly, k should not repeat unless the random number generator is broken.

Considering that k is generated at signing time and should be random, we can conclude that whoever chose k for those transactions has a faulty random number generator which is either outputting a fixed value or a small value which increases the probability of k being repeated. There is no good reason for this to happen, so this error comes from either a faulty RNG or a completely misunderstanding of how ECDSA works.