From August 2017 to early 2018, Bitcoin’s blockchain split several times (i.e. hard fork), resulting in two coins, running on two separate blockchains.
the chart is misleading and this statement is absolutely wrong.
bitcoin's blockchain never split at all. it has been growing as always as a singular and immutable ledger.
what this is referring to is creation of
copies. since bitcoin's both source code and blockchain are open and free to copy, lots of people during the 10 years have copied it and created their own
altcoins none of them mean "splitting bitcoin's blockchain"!
as for the chart, it is misleading because it is ignoring the most important factor that is inside the line it draws on it and calls them "BCH and BTG".
that line coincides with the end of a debate that was going on for at least 3 years called "scaling debate" that had damaged bitcoin a lot and had prevented the growth for a long time. when it finally came to an end in August 2017 with activation of SegWit, the confidence came back to the market and investors started buying bitcoin and that was the reason why the price went up.
if anything the dozens of garbage fork coins such as BTG, BCH, BPrivate, BSilver,... prevented and slowed down the rise by a lot.