I'm sure the team's extremely poor start is a combination of several things that have unfortunately come together to impact the team negatively. Lack of preparation in ST, playing with a sense of complacency, the brutal west coast schedule to start the season, and Leongate have already been mentioned many times.
Another factor is just plain, good old randomness or luck, as is suggested by the following stats, courtesy of my man RedSoxStats:
Compared to last April the Sox are striking out, walking and hitting home runs at an identical pace. Their barrel or solid contact was 15.1% and it's 15.5% now. Their doubles are WAY down. Their BABIP was .316, it's currently .272.
2018: 17 games, 5 HR allowed on mid-mid pitches
2019: 17 games, 16 HR allowed on mid-mid pitches
Last year, lady luck was on our side to open the season. This year, not so much.