They may have 10k applicant from the start. But...
When you start with the application a computer will scan and sift through looking for relevant keywords and if that criteria is met. Ok some will fail there.
Congrats! Your invited to do online assessments. Complete the questionnaire and math test... Many will fail here.
Depending on the TOC and order they do things. Another more in depth questionnaire, or a telephone interview or both. Some will fail.
Already more than half will be gone by now. Then you factor in the actual assessment from OPC, interview and medical. By the time you get to the end not many people are left.
The reality is many many people apply to the role as it is always advertised in the media etc. They always mention the salary and how you don't need any qualifications. Which is why these job are so competitive. But what people don't realise is the sheer level of work and responsibility to get that key. The amount of times I have had a friend of a friend or someone tell me that all you do is push a lever.... I then invite them to do the tests if they think they know the job.
Of the 10k applicants only a fraction have the actual qualities. I guess what I am saying is that you have all found this website. Am active here and have showed willingness and determination that you want the role. That alone will make you go far.