Two issues came into play here... One, AB 5 caused the need to W2 coaches and increased related cost. Two, most soccer clubs have part-time secretaries or people handling administrative issues... or even worse, they have a soccer coach handling it. The idea was to create an organization that can serve all the various administrative needs for a soccer club. That's about it. Pats and Arsenal staff are friends so they worked together to create Sporting. There is no merger or anything like that... basically, now they share the same some of the same secretarial or administrative staff only where the club needs that specific task out-sourced. For example, they could have separate Registrars but could use the same individual to oversee uniforms.
It's not a bad gig from a parent perspective if you've ever ordered uniforms and waited 17 years for your jacket to show up. In an ideal world, the sporting staff would be competent as you are now able to hire a qualified person who is able to be full-time/paid appropriately because they work for multiple clubs rather than part-time for one. Plus, it gets parents out of the picture... no more... I'll design your website if you waive my little darlings fees for the year... where a club waives $2500 in fees for a $300 task. lol.
Also, there are numerous other clubs utilizing Sporting, locally and around the US. It also involves a partnership with a conglomerate of European clubs but the effect of that remains to be seen.