the chase/jules disconnect is because of changes in the tlc team. chase originated in word and math detective, which were the last ones developed by brøderbund. the brøderbund team stayed largely in place immediately after the tlc acquisition, which is why he's still in thinkquick (and why carmen is still voiced by mari devon, but the other characters have VAs from the cluefinders games).
shortly thereafter tlc was bought by mattel then spun off to riverdeep. most of the people working on the games either quit or were let go, so treasures of knowledge had a completely new team working on it. hence the creation of jules and hawkins and the return of the chief. also why irene trapp (jules) was the only major va from previous games (thinkquick, specifically) to reappear, though christiane crawford (carmen) had been one of the bit part VAs in where in the usa.