Although difficulty adjusts to try and make a block be mined every ten minutes, it isn't a sure bet. If you look at the timestamps, 767807 came out in the same minute as 767806. This is because sometimes a miner just gets incredibly lucky and finds a solution for a new block immediately without having to do much work. It's uncommon, but that's just how probability works.

Now, the reason it is blank is because of a small quirk in how most mining pools function. A pool coordinator will send miners a blank block template with no transactions on it, and then they fill in transactions as they go. But if a miner gets really lucky and finds a solution for the blank template, they will sometimes publish it before any transactions get added.

Mempool.space does actually have an explaination for this in their FAQ. Hopefully this explaination helped though :)

просто нахождения блока без транзакций выгоднее во времени. не нужно тратить время на загрузку всех транзакций и искать блок. дешевле найти блок сразу и без транзакций. но комиссии исключены. это не запрещено. пока что выгодно. все нормально

No blocks are empty. All blocks contain at least 1 transaction. It's the block reward paid to the miner who found the block.

Often it's because a miner is running software where it mines en empty block until a new block with transactions is created. Used to be quite common now quite rare.