Is it corrupt if a person who works as as Special Adviser to a Minister, persuades the Government Department he is working in to hand over half a million pounds to an organisation run by a previous adviser to the same Minister, and then goes off and works for - and gets paid by - that same organisation?
In fact, in this case it's even worse.
Shortly afterwards the Government cancelled the previous government's 'Building Schools for the Future' scheme. So money that had been earmarked for renovating thousands of state schools was siphoned off to an untried, untested - and socially divisive - scheme, specifically designed to subvert the state system.
And then Cummings went off to work for his friends at the NSN, who paid him with the money he had steered their way in the first place.
See Wikipedia on Political Corruption, especially this section on 'kickbacks'.