Bitcoin Core's standardness rules limit transactions to 100000 vbytes (or 400000 WU). Larger transactions are not relayed or added to mempools. Since they are consensus-valid, they are obviously acceptable if included in a block however.
The purpose of this rule is DoS protection against a few known (such as quadratic hashing) and possibly unknown ways to trigger excessive computation at validation/relay time. They also help block template building for mining, as it's easier to fill up a block with many small transactions as opposed to a few big ones (binpacking problem).
What limits prevent this transaction from being relayed?
Transactions size standardness limit.
Is it configurable?
Not in Bitcoin Core, no. Standardness limits are just a policy rule however; anyone can run any software, including software that doesn't have such a limit, or has it patched.
What units are used (absolute size or weight units)?
Is there an associated fee rate limit that also applies?
Independently, transactions whose feerate is below 1 satoshi per vbyte are not relayed either.