In the last few years, his organization initially founded to support bitcoin core development monetarily, spiral.xyz, has become the most major source of funding for bitcoin developers and related events.
Source: https://xkcd.com/285/
Jack Dorsey has also invested in chip manufacturing and claims to want to fundamentally change bitcoin:
https://www.datacenterdynamics.com/en/news/jack-dorseys-block-inc-reveals-potential-upgrade-on-industry-standard-bitcoin-mining-rigs/
https://www.datacenterdynamics.com/en/news/jack-dorseys-block-inc-reveals-potential-upgrade-on-industry-standard-bitcoin-mining-rigs/
After reading that article/news, it seems he actually wants to improve efficiency when someone mine Bitcoin partially by introducing modular and re-use property. I don't see anything that could change Bitcoin fundamentally.