Blaming tag managers and marketing departments is quite common and yes while they are problems on some sites many developers overlook the impact of their technology choices e.g. client side rendering, JS based components etc
There's a reason why I speak of "third party", though I guess it might be unclear in english - my bad.
There are three parties involved in the bloating. Management prioritising certain things is one. Developers (including here both programmers and designers and others etc.) not caring enough or otherwise making choices that lead to bloat is second. Marketing team with power to require problematic things added or just going crazy with tag manager is third.
