How does block propagation delay not cause accidental forks?
How does bitcoin prevent accidental forks like this?

It doesn't. Bitcoin make little effort to prevent forks at a technical level, instead relying on the fact that when a fork does happen, it can be resolved by waiting for additional blocks and picking the chain with the most work.
As Pieter mentioned, the mining mechanism itself prevents long term forks. The act of mining extends one chain beyond the other, reducing the shorter chain to a temporary and now discarded fork.
For miners specifically, they put in a lot of effort to avoid this - mining on even a minor fork is inherently risky, as they could lose their blocks if the other side of the fork wins, thus losing the block rewards.
To reduce this risk, all serious miners join high speed links as Bitcoin Fibre. These are specially designed to minimize propagation delay.
No serious mining operation will be looking at propagation delays of 122 seconds - those would only be happening at nodes run by people with absolutely abysmal peering and internet access. For the vast majority of nodes, blocks are received in a few seconds, and for miners, usually in &lt;1s.