While you may be able to point to one or two anomalies, we need more than that. If the MPA has the ear of 70% of congress, that's still enough to have their way on legislation, regardless of a few fringe elements.
is not necessarily incorrect. But it is also possible that it is the other way around:
being popular => receiving funding => winning
I.e. candidates which are more popular tend to have an easier time receiving funding. Or, it could be some combination. This would also explain the outcomes you point to.
As far as I can tell, there's not a large trend that this is changing currently. The candidate that spends the most still wins 70-80% of the time: https://www.opensecrets.org/elections-overview/winning-vs-sp...
The cost of running a winning campaign has steadily increased as well: https://www.opensecrets.org/elections-overview/election-tren...
Those trends, to me, do not paint a compelling story that things are different now.