In my own experience, if all the voting systems rigged to benefit size, there is a broader phenomenon of larger parties existing which which are usually in power (though often in cohalitions) and which attract the kind of people with no scruples who go into politics to become wealthy from selling access to power (i.e. the corrupt).

However in the two other countries I lived in beyond the UK, one of which had Proportional Vote and the other Multi-representative Electoral Circles (so, not as bad as FPTP, but still Mathematically rigged), I have not seen a case of the larger parties being obviously taken over as means to get to power like I saw in the UK, though I’ve seen smaller parties being created and/or supported by foreign money and then eating up some of the vote of the large parties.

Certainly were I am now - Portugal, which has Multi-representative Electoral Circles - of the two new Far-Right parties which were created not that long ago, one of which for sure got money from the Fascists in Brasil and the other also likely had funding from abroad (the campaign phamplets and other materials in their very first elections were both far too expensive for a small party and using the kind of design and slogan style one finds in International Marketing campaigns in huge contrast with other small parties), probably American (they’re an ultra-neoliberal party created a couple of years after Steven Bannon came to Europe with money he openly said was to fund far-right parties), though there I don’t know for certain. Both of those parties are taking votes away from the large rightwing party but also partialy from all the way into the leftwing (the more Fascist of the two is even picking traditional working class votes that used to go into a Communist Party)