So ITV is missing a 24 hour news service (had one a few years back) and a handful of radio stations .... well that obviously warrants 23000 more staff. LOL
Lets put it this way.
News gathering is very resource intensive if you wish to do it properly - which is why ITV use ITN (it effectively means they don't have to employ many/any news gathering staff themselves, whilst ITN also provide the news gathering for other commercial operations).
So ITV's staffing is down something like 3000 just by outsourcing news, something the BBC can't do as it's a key part of it's charter.
Running a radio station that does more than just 15 minutes of "local" news per day and selecting a play list takes a lot of staff.
Radio 4 for example has no equivalent in the commercial sector in the UK because it requires a lot of staff and money to do the sorts of programming it airs.
In effect it's a full time TV station like BBC1, with just the visual side of things missing.
And you're completely ignoring one of the biggest differences, namely the amount of content produced in house.
The BBC directly employs a large number of people to create programming in house, and making even a short TV programme takes a lot of people.
The ITV figures won't include many staff who actually create the content, as they buy most of it in.
At the moment your staffing figures are like comparing a Primary school with a University in terms of what is done and the staff needed.
So it's not really surprising that the BBC employs something like 5 times as many staff as ITV, it has considerably more new output per day than them.