Sforno on Numbers 8:4/ספורנו על במדבר ח׳:ד׳

1וזה מעשה המנורה מקשה, the very composition of the menorah as a single chunk of gold, with all its lights facing the lamp on the central shaft, symbolises this united endeavour to serve G’d, i.e. to look towards the spiritual light as symbolised by that in the center of the menorah, its “trunk.” המנורה מקשה, to underline the unity, the whole people jointly striving to attain the same spiritual objective.