From my seat at ParcPlace 1993-1996, I'd offer the synthesis: ParcPlace's legacy-enterprise-apps-focus prevented it from properly chasing the pure-internet opportunity that Java pursued.
ParcPlace had a successful 1994 IPO based on the high-price, deployment-licensing enterprise/legacy-apps market, & had configured itself with sales force & execs having a particular kind of seasoning. From there, how do you reconfigure, & bet the company, on another hypothesized future markets? (It's nearly impossible.)
And yet, ParcPlace soaked up so much of the Smalltalk expertise/mindshare, & even more after the Digitalk merger. IBM's VisualAge offering had a similar high-end focus. So no Smalltalk team of critical mass could fully chase the markets, & positioning, that Smalltalk's cousins Java (& later Ruby via Rails) did.
When Smalltalk needed a champion with the resources to develop it into broader & newer markets, the potential champions – both technical & business – were all distracted, diluted across projects, or (quite rationally) pursuing other lower-hanging fruit that offered more immediate legibly-capturable value in the mid- to late-90s.
Something like an inspired, before-the-curve embrace of open-source & shared-standards might've earned Smalltalk, the language, a bigger future through to today. But those actions might not have earned the then-extant relevant actors enough, soon enough, for them to have thrived or even survived.