It continues to amaze me how many 'people' in tech are in denial about the 'bot problem'.
Manipulating algorithms is an arms race. If you have written an algo that can be influenced by clicks alone, its only a matter of time until the algo is abused.
Stage 1: Full-time Clicker for Hire
Easiest way to get started. One person manually taps all the phones to fulfill the order. These farms will install any app, create numerous accounts, and tap any sequence on screen that the client specifies.
Stage 2: Command and Control Nodes
Using ADB and other debugging tools, farmers can puppet hundreds of devices programmatically using a central command and control server. This arrangement is way more efficient at completing tasks in parallel.
Some farms may chose to virtualize their 'phones' at this stage. However, a virtual machine cannot get an IMEI (needed for activating SIM, required for some identity verification tasks). Additionally, apps can detect if they are being run in a virtualized device and block certain actions. Bare-metal phones are the gold-standard.
Stage 3: Clustered Phone PCB Servers
Custom rack-mounted enclosures with custom power distribution and video emulation. Each of these servers can puppet dozens of phones using only the phone's PCB. These setups are ultra space-efficient and use less power because they don't require the screen to function.