But they are not hiring worldwide. Their openings clearly state: UK (and remote, within UK). So, I don't understand how they are hiring in the UK with such low salary ranges
Ah, didn't see that. Tech companies contradict themselves (or otherwise say patent nonsense) in job postings all the time, unfortunately.
By default these job boards seem to often be clusterfuck operations, with everyone shoving random detail into the reqs and no one there to curate the resulting message.