Can I connect 2 motion detectors with one power supply to a single LED Strip?
Yeah, that will actually work.
I mean, the way you wired it would be a horrifying hack if it was mains AC power.  That would be a “loop”, and those are very bad (in AC) because everything inside the loop becomes inside the core of a transformer.
That’s not a problem in the DC domain.  (Mind you I’m not sure that doesn’t change if you use PWM dimming, but I’m not going to tell you to worry about it).
I recommend you bring a 3-wire cable between the two PIRs:

Positive
Negative
Switched Negative (assuming you switch negative; that’s best practice with LED strips).

And then, feed both positive and switched-negative to the LED strip at both ends.  That way you are not relying on the thin little pathways inside the LED strip to carry all the current.  (There’ll be noticeable dimming if you do).
By the way, learn the fine art of cutting LED strips to length; they have specifically designed cut points.
It will also aid your craftsmanship to learn to splice and/or solder, so you aren’t dependent on cheapie connectors and premade wiring harnesses.