I've long considered it an inherent part of the Inner Sphere's pseudo-feudal governmental system. You might be a hotshot Coordinator or First Prince, but there are people under you who are power-hungry bastards and will happily replace you if possible. Feudal systems have always had to strike a balance between defending the realm, and keeping the nobles from gaining too much power.
You don't want your cousin, Duke Backstabber, to be able to churn out as many Warhammers as his factory will produce. Oftentimes it's more important to keep him from growing his army than it is to have that army at your disposal. Yeah a couple extra mech Divisions would be great, but not if they're under his control (and they would be). So you're gonna make sure that your fusion engine factory is always experiencing a supply shortage when the Duke comes calling. "Sorry buddy, I can only spare 10 engines this year..."
Basically everybody is doing the same thing back and forth to each other when it comes to mech production. It's not all technology loss.
eh, not QUITE.
Feudalism is just a term. The actual function is when you have centralized control over some vital resource (in the middle ages it was arable land and the ability to employ force) and that control has devolved to a hereditary structure with limited to nonexistent movement upward in the social strata.
If you can think of anywhere infamous for needing 'connections' to rise? it's the same thing. You can have a Feudal system where everyone has corporate titles, or where everyone has "elected" titles. it's the mechanism. In a Feudal Society, the State controls the vital means of production, and has a monopoly on the legitimate use of force, AND requires Fealty while also encouraging Hereditary ties when distributing authority (IOW, you have to have an insider 'invite' you in before you can move up in society).
You can get a Feudal condition in a Bureaucratic state, it's all about how power is centralized and distributed.
basically, if you can be born in poverty, and build or buy your way into the upper levels of power without being married to or related to, or best friends with, someone in power? you probably don't live in a Feudal state, or you live in a weak feudal state.
The other big indicator is if your distribution curve is triangular, or diamond shaped. what I mean by this, is in a triangular wealth distribution model, your largest 'class' is the lowest-the majority of your population lives in effectively poverty, in a diamond shaped distribution, you have a small percentage that is genuinely poor, a large middle class, and a small elite.
Typically it's easier to rise in a diamond graph, than in a triangular graph.
Notably, Feudal systems regardless of title origin tend to be triangular graphs. (vast population of serfs, middling population of craftsman and merchants, small population of a given elite.)
There are no diamond-graph states in the Inner Sphere OR the Clans. They're all heavily centralized with control of one resource or another in the hands of the same ruling class that has a monopoly on the use of force, whether that small group is ostensibly elected (OWA, Taurian Concordat, etc. etc.) or appointed (Magistracy, CapCon, LC, FWL) or openly inherited monarchy (Federated Suns) the core shared characteristic is that like the Clans, that elite is very small, and like the Clans, the lowest class is also the largest class in raw population numbers, while also having the fewest rights and protections.
like the OWA, the Free Worlds League is a 'cosmetic republic'-meaning they have ritualized "elections" that put members of the same family in the same position generation after generation. (this is also true of the CapCon and, to an extent, the Combine-though the Combine's model is a more honest Military Junta model-they don't PRETEND to have elections.)
In the Lyran Commonwealth, the Archon is
technically answerable to the Estates General, but...again, the position is just as hereditary as it is in the OPENLY Monarchial Federated Suns.
in the end, the real question tends to end up being; "How shitty is your life at the bottom of the pyramid?" that ends up being your only REAL measure of difference between the various states and the Clans-in terms of government.
what ends up, is that it's shittier in some places, than in others, or it's shitty in different ways. (one state might let you have a technical free speech, while the Lords enforcers may use technicalities in other behaviours to punish you for it, while in another state they're honest about delivering that midnight knock on your door with a trip to sleep with the fishes for posting that disrespectful meme on 4Chan, or even so direct and clear about what kind of universe you're inhabiting that they bill your family for the rope they hang you with or the bullet that was put in your brain for shooting your mouth off at the wrong time in public.)
which all circles the bowl back to the 'technology loss'. In highly centralized systems you get a high level of both official, and unofficial corruption. Yes, graft, and sweet sweet corruption. This can range from "They pretend to pay us so we pretend to work", to using materials, parts, and production delays as political weapons to topple ambitious cousins/aunts/uncles/siblings, to leeching off of a system that hasn't been competently run for generations and 'looking out for number one' at the expense of everyone around you. (Mandarins, Social Generals, Petit Nobility, and so on.)
The Tech wasn't "lost", it may, however, have become buried in layers of apathy, graft, internal theft, black markets (because any time you restrict something, you will create a black market), intentional sabotage, porous security, more apathy, contrary ambitions, unscientific scientificism...take your pick, it's probably all of that and more.
After all, they pretend to pay us, why shouldn't we pretend to work?