"Why?" you ask. Imagine this hypothesis: Part of the hype for machinimas was due to the fascination of newfound, groundbreaking computer technology, which has dissipated. Secondly, machinimas are becoming less distinguishable in style.
With the continual growth of computer technology in the 2000s came "realistic" features in games: sharper textures, better shaders, better animations, more-detailed maps, smoother models, face muscles in NPCs, and most importantly: real-time physics. Such new technology was groundbreaking for video games, and there was a lot of hype in gaming communities over these fresh features. Along with these features and their hype came a much wider potential for "machinimas", videos produced using game engines as a medium.
Take the "Red vs. Blue" series (2003) for example. Originally produced on Halo (2001), it took advantage of NPC animations and vehicle physics to keep things more interesting than just players talking. Furthermore, although frag videos from Quake, Team Fortress, and other communities existed, the concept of machinimas telling stories and punchlines was barely explored by 2003.
Also, at this time, the average gamer didn't have computer specs efficient enough to capture game footage with passable quality, and such software needed to capture such footage was usually behind paywalls.
Then came along Half-Life 2 in 2004. Valve's Source engine, which Half-Life 2 was built upon, introduced a variety of revolutionary graphical features hardly seen before, more importantly: facial muscles and real-time physics (including ragdolls). Such a high-end engine for its time demanded better computer specs, which made the production of machinimas a much higher possibility for those who upgraded. Valve's engine also carried a variety of console commands that can easily manipulate its supported games, such as NPC's AI and animations, physics, and other features of interest.
If that wasn't enough for potential producers to be interested, the introduction of Garry's Mod (2004) changed machinimas as we know it. This sandbox game allowed content from Source games to be loaded and played with by a variety of tools, and worldwide third-party contributions added a variety of custom models and maps. Ragdolls and NPCs could be physically manipulated and posed, and any prop or map could be spawned and set up for production design: all just from using a weapon. Most importantly, Garry's Mod introduced the usage of multiple cameras, allowing producers to simply be a self-dependent, 1-man job.
This was a magical time for machinimas, and the relatively-new YouTube couldn't have served better as a distribution platform. Gmod videos began flooding the Internet in 2005, if not earlier. The hype of Source's groundbreaking features empowered these videos. Not only did Source's games help further popularize machinimas, but people also realized the potential of machinimas as a medium. Slapstick, "random" comedies took great advantage of the physics engine and were at the forefront of the popularity, such as "Shortbits" (2006), "Half life TV" (2006), and "The Big Random Gmod Movie of DOOOOOM!" (2007). Other machinimas invested more in lip-syncing technology ("I'm Still Seeing Breen", 2006) and production design ("War of the Servers", 2007).
By this time, "machinimas" was a common term and had proven to be a capable medium for entertainment. In fact, a YouTube channel named Machinima opened and became a common source for such videos. The idea of producing with video games was still a relatively new concept to most, and people produced videos with any game they could capture with.
I, myself, was inspired by the early influx of Gmod videos and started producing my own machinimas in 2006 before pushing further with my "UnKnown Moments" series (2007-2012) and other titles.
Tools specifically designed for producing machinimas were eventually created, such as Valve's Source Filmmaker and Halo 4 and Grand Theft Auto 4's replay systems, allowing machinimas of higher quality to be produced easier.
While machinimas live on (and likely always will), the golden age has passed. With machinimas' increasing popularity also came an oversaturation of mediocre videos, indistinguishable LPs, and predictable frag videos over time. The Machinima channel itself gradually focused less on actual machinimas and gave trouble with its content creators, and with the increasing performance and graphics of computer technology, the idea of machinimas became less exciting and more of a common form. This commonality extends to games' replay systems, which often prevent machinimas from having unique styles due to limitations in cinematic customizability (depth of focus, camera movement, etc.).
Call me a hipster, but I found machinimas to be much more interesting 5+ years ago simply because it was still a relatively-new medium and people's styles varied more. If I were to produce another UnKnown Moments, it wouldn't have the same atmosphere simply because the fresh concept of machinimas, along with physics and other features, has dissipated since those days.
Maybe it's just me being old or some shit. Either way, it's just my opinion.
