This comment made my week! Ty! I'm glad the video was helpful!

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Thanks for the question! The factoring solution space is not infinite, but it is exponential (or worse) with the number of bits in the keys. Here's an almost 2000 year old algorithm that will factor any number into its prime factors, given enough time to compute: en.wikipedia.org/wiki/Sieve_of_Eratosthenes. The challenge with conventional computers is that the key size for RSA today is 2048 or 4096 bits, so you are looking at O(2^2048) size search spaces, which is unsearchable in anyone's lifetime (and the reason no one is breaking the RSA keys directly). One of the foundational algorithms for quantum computers is Shore's algorithm (en.wikipedia.org/wiki/Shor%27s_algorithm), which in the best case can factor large numbers O(log 2^2048) which is roughly O(~600), a much more achievable complexity! Today's quantum computers are still too immature to factor large numbers, but as the technology improves, there may someday come a time when a quantum computer can brute force discover an RSA private key, which would be pure chaos for the internet because anyone with a quantum computer could pose as anyone else on the internet (and create their digital signatures, etc...), so cryptographers are busy at work today to develop asymmetric key ciphers that utilize one-way functions that are not amenable to any known quantum algorithms.

AES-256 is not going to be broken by a quantum computer for a very long time.