He used the state-of-the-art technologies of his time: oil paint, etching.
He was a commercial artist, making portraits, etches to sell. Etching was the best way to make many reproductions of a work of art.
Rembrandt also made his own art materials. You can see pieces of egg shell in some of his paintings. When etching, he developed a new method, using wax to coat plates so he could use much looser lines.
He was interested in storytelling. He really wanted to make these paintings that depicted biblical scenes, but portraits of rich people brought in way more money.
Commercial. State-of-the-art technologies. Making his own tools. Telling stories.
Would he be a film maker today? Would he be making his own cameras, or creating his own render farms for special effects?
He went bankrupt, spent way too much money in his time. He’d probably be notorious in Hollywood for not sticking to budgets.