Those could be the reasons why Bitcoin's market dominance has been rising at an exponential rate. Since it's the first cryptocurrency that came into existence, it has managed to gather a lot of attention within the mainstream world. All the eyes are within Bitcoin's latest developments as it could affect or benefit other cryptocurrencies in the space. Compared with other altcoins, Bitcoin has the most level of adoption among merchants, businesses, and individuals alike. Not to mention, its development and innovation is far superior than most well-known altcoins in existence today.
I wouldn't exactly say exponential though. If anything, these 2019 highs are probably a build up to a maximum of 75% or 80%, but we'll never see more than that, and never for too long. Even a maximalist has to agree that a culling of say 90% of altcoins might take Bitcoin dominance up a lot, but that kind of crypto fallout would also affect Bitcoin price, diminishing its dominance.
This is the scenario for the next few years anyway. I do believe at some point, Bitcoin will be one of very few to survive and strengthen, and "cryptocurrency" will again be synonymous only with the few that find actual use among everyday people. All other tokens will be negligible in the ocean of Bitcoin.