I think you may have misunderstood.
Actually, Richard Sturdy launched the first ever officially deemed PTC program. That wasn't in the 1990's, by the way.
Altho John had worked online many years dibbing and dabbing with this and that, he eventually launched StormPay which was by the way, a very good payment processor. Unfortunately, people don't have all the facts about StormPay and when their not in the know, they some times tend to holler scam. Your topic is not about StormPay, however. Anyway, John implemented a little PTC within StormPay as an additional way StormPay users could use funds for advertising...plus John probably did a bit of advertising himself as most program owners do.
It wasn't long that the light bulb went off in John's head. He saw how much the StormPay users enjoyed the PTC area that he implemented. Therefore, he came up with the idea to launch a full fledge PTC with all the bells and whistles. Hence, ClixSense was launched.
Keep in mind, altho the original PTC that launched by Richard some years before, was the first, it was and has never been, deemed the start of the PTC craze. In fact, WL was sort of slow in achieving the recognition it deserved.
After ClixSense launched, it became very popular very quickly. As marketers and programmers and what have you viewed it, they wondered how they could do the same...as is the case with most any suddenly popular program, people try to copy it.
PS. By the way, ClixSense was very trusted from it's start. People joined it left and right like and their data base grew rapidly.
Now I could sit here and name program after program, in exact order by the way, that launched after ClixSense do to the 'ClixSense Craze'.
BuxHosts (nextgen) certainly did not lead the way, in fact, they were mighty late in the game. Since BuxHost, is inexpensive hosting and inexpensive scripts, everybody and their bro and sister appear to launch them. Unfortunately, it takes a whole lot more than just shelling out the dough for hosting and a managed script to succeed with those...that is why the majority of them fail..and fail very quickly.
There was no PTC's at all in the 90's. None.
ClixSense really did in essence, begin the 'PTC Craze' altho ClixSense was Not the first PTC to launch.