I don't see how getting enough protein on a vegan diet would be a problem, especially when you mention plant-based protein powder. I think healthy calories may be an issue if you don't include nuts and seeds, but as long as you cover your energy needs from vegetable sources you get enough protein and enough of all essential amino acids. You didn't mention this, but protein combination is a myth, and only very few vegetable sources lack certain amino acids. So does some animal sources as well, but that is almost never reported.

You didn't mention this either, but if you want to avoid protein powder, it may be harder to find lean protein sources. I just looked up nuts (peanuts specifically), that have 27% protein but also 51% fat. Chicken breast also has 27% protein, but only 8.7% fat.

I'm not a body builder and haven't investigated how to go about it in detail as a vegan though the full cycle of bulking and shredding, but if you just want to gain strength getting enough calories and protein shouldn't be a problem. I've also read that most body-building magazines completely overestimate how much protein you need, citing numbers four times what sports science says.

You have first-hand experience in this situation and I'm clearly speculating, but perhaps you didn't get enough calories rather than enough protein? Of course it all depends on what you're eating. When some people say vegan food, they mean raw food or mainly vegetables, while others include a lot more legumes, nuts, and seeds.