Not an accident at all.

There really isn't any incentive to include transactions in blocks.
It's a modest amount of processing power required to test, pick and commit transactions to block (nearly a quarter of the bitcoin codebase is dedicated to this).
On top of that, if the node is behind a slow WAN connection - the time to propogate the block across the network could very well mean it is beaten by a more responsive node.
You could argue that the fees are the incentive to include them in a block, but when you are talking 6.25BTC ($184,000 USD) as the base - some aren't bothered by this.

Another possibility is the stratum/pool mining software responsible for this block is not connected to a full node, rather a lite or SPV node. To build a valid block, you really only need to know the previous block hash, the height and the coinbase reward. Running a bitcoin node again, is quite resource intensive - and the disk space alone is 405Gb (standard, not txindex) - I can fully see a situation where some clever software simply listening to the headers could work.

There are much more devious reasons as to why the block has no transactions, but will leave them to the readers imagination.
The majority of it stopped around April last year (2021) *cough*.

james