A lot of "butt-in" interventions are there not so much in a constructive manner to try to find the best contract but to interfere with the opponents' bidding system, which is usually less equipped to deal with it.
Pick up most bidding systems and it can be pages and pages of bids and responses and rebids etc, and very little on what to do if the opponents come in.
The intervener does of course take a risk but hopes to get away with it, especially as the opponents have not necessarily yet ascertained their holdings and may therefore prefer to continue by showing their partners what they have rather than going for penalties.
The real downside of the intervention is that when the other side does eventually win the hand, they will often be able to place the opponents cards better.
Methods like DONT over a strong NT, (and most of the other bids made over a strong NT) are good examples.
In the early 1990s I recall the top international teams were quite aggressive. The Poles in particular. Opening strong pass systems were not uncommon. If you're able to find archives of old tournaments, the 1991 Bermuda Bowl final between Iceland and Poland might be quite interesting to analyse. Of course you have to bear in mind that the Bermuda Bowl is a "teams" tournament and the final is over a lot of boards, and played against a team who has your system notes and has studied it well.
In a match-point pairs event which is a win or lose situation, where a mishap gets you "only" a bottom (but can potentially be recovered quicker) and against opponents who only see your system card in the last moments, one can often be more aggressive.
In the mid-1990s the "Law of Total Tricks" was popularised by Larry Cohen, and Robson & Segal's "Partnership Bidding" was published, primarily about competitive bidding and I think these two publications improved competitive bidding in general among the middle-skilled bridge players. (Decent club-level players who are not international / Bermuda Bowl standard but are not novices either).