I'm glad you're playing devil's advocate, and you're not wrong in that a single player could have multiple accounts, this was especially true on the Ongame network, as it provided the platform which sites could whitelabel to run their own poker room, with individual promotions/branding etc, while leveraging the benefits of a large shared player pool.

The thing that stood out was the length of the sessions played by these players. The regular professionals (regs) would play multiple tables at once, usually 4-8 tables (Ongame software was shitty and prone to crashing) for a few hours at a time (poker is mentally taxing). These guys were playing 8-12 sessions on single tables.

In terms of amateurs, I'm not taking offence, but many of us were playing full time for a living at the time, and their winrates were beating many of us, without any game selection (explicitly choosing to play with weak players).

The strategies were indeed novel - the one I can describe in layman's terms - they never just called a bet before the flop, they always folded or reraised. This is a huge paradigm shift from all conventional wisdom at the time, and a strategy that is very difficult to execute well (hard to go into details without getting into poker terms/theory).

While poker strategy was (and still is) constantly evolving the overall stats/strategies deviated so far from the norm that we all agreed we were up against a bot. Again, without going into details the strategy had a much more mathematical/game theory approach than the far more commonplace exploitative strategies that everyone was using at the time.