I'm not convinced that they were that invested in Neil and think that he came as a package deal with Katya back in 2016. After 3 years on the bench, they probably felt that they kinda had to give Neil a partner for the 2019 series and saw Pasha's departure as the ideal opportunity for Neil to get a spot. What they probably didn't anticipate was that they only signed 7 female celebrities and most of them were taller than Neil, Kevin, Gorka & AJ.
With their obligation to give Neil a partner and the other two being pros that have always made it far, that left Gorka out in the cold. As it stood, Neil didn't really 'take off' as an audience favourite and with both AJ & Kevin out this year, Gorka got his spot as a main pro back. I am kinda surprised that Neil didn't get a spot this year but if it was a choice between him & Gorka, it's easy to see why they chose Gorka for a number of reasons. He probably got Maisie as a 'reward' for being on the bench as whilst she is annoying, she is probably a golden ticket to the final.
Don't like the benched pro thing either, should only be for the newbies who need a year or two before being ready to have a celeb.